Officials say the blaze is out and no injuries were reported, but investigators are still working to determine what triggered the release and fire.
PASADENA, TX— A fire at LyondellBasell’s Bayport Choate chemical plant drew a heavy emergency response late Thursday, sending flames and smoke over the industrial area near Choate Road as officials said all workers were accounted for and no off-site protective action was ordered.
The fire was reported around 9 p.m. on March 12 after what the company and emergency officials described as an operational upset or process upset at the plant. By early Friday, local emergency managers said the main fire was out, though crews stayed on site and one smaller fire was still being managed within the facility for part of the day. The immediate stakes shifted from firefighting to cause, air monitoring and the size of the release, with public concern rising even as officials said community monitors showed no actionable readings.
The known timeline begins before the visible flames. LyondellBasell later said a unit upset started around 7:45 p.m., setting off the site’s emergency flare system as equipment relieved pressure from tanks and columns holding flammable gases. Sometime afterward, a fire broke out near the continuous flare system, which the company described as a piping fire. By about 9 p.m., the incident had become visible outside the plant, and nearby residents along the Ship Channel corridor began posting photos and video of large flames and smoke. Emergency messages warned that people in the area might hear sirens or rumbling and might see bright flames, smoke and responding vehicles. Fire crews from the plant, nearby departments and mutual-aid partners moved in while local officials said no evacuation or shelter-in-place had been ordered. By 6:42 a.m. Friday, the La Porte Office of Emergency Management said the main fire was out, though activity around the facility would continue as the response shifted into monitoring and investigation.
Several important facts were established quickly, while several others remained unsettled. Officials said no injuries were reported, and the company said all personnel were safe and accounted for. Harris County Judge Lina Hidalgo said overnight that first responders were working to close a valve releasing a mixture of chemicals, a detail that helped explain why the response continued for hours after the initial fire. The Harris County Fire Marshal’s Office later said the facility had a process upset that released flammable product, which was ignited by the pilot light of a flare operation. That statement offered the first public explanation of how the fire may have started, but it did not answer what caused the upset itself, whether equipment failed, or whether operators were dealing with a larger process problem before the release. LyondellBasell said the root cause could not be pinned down before a full investigation. ABC13 reported that the fire marshal told the station two tanks caught fire. The company, meanwhile, described the incident more narrowly as a fire near the flare system. Those accounts are not necessarily inconsistent, but they show that the exact sequence inside the unit was still being pieced together as of Friday night.
By late Friday, the picture of what burned became clearer. A company incident summary cited by local reporting said the fire involved more than 20,000 pounds of flammable process gases, including more than 15,000 pounds of n-butane along with isobutane and carbon monoxide. Under Texas reporting rules, that early estimate is still preliminary and can change as the company refines its calculations. That matters because the Bayport Choate site is not a small terminal or storage yard. It is a major chemical manufacturing complex that produces propylene oxide, propylene glycol, propylene glycol ether, tertiary butyl alcohol, high-purity isobutylene, tertiary butyl hydroperoxide and ethyl tertiary-butyl ether. Reuters, citing the company’s site description, said it is the largest propylene oxide and tertiary butyl alcohol site in the world based on production volume. The facility has operated since 1969 and was expanded in 2022, according to local reporting. Its size and product mix help explain why nearby residents reacted strongly to the sight of flames, even after officials said the public was not in immediate danger.
Air quality became the next major point of tension. Harris County Pollution Control deployed monitoring around the site, and local officials repeatedly said no actionable readings had been detected. KPRC reported that county monitoring did not show dangerous levels at ground level and that no protective actions were needed for surrounding neighborhoods. Even so, some residents and advocates said the official reassurance did not erase fears shaped by years of industrial incidents in communities along the Houston Ship Channel. Jennifer Hadayia of Air Alliance Houston said neighbors who saw flames outside their windows wanted faster and clearer answers about what was burning and what might be entering the air. The gap between visible danger and measured ground-level readings is likely to remain part of the discussion after the fire. Monitors can show what is present where they are placed, but those readings do not by themselves answer every question about the path of a plume, the height of emissions, or what may have burned during the most intense stage of the event. For now, officials have publicly stood by the conclusion that conditions around the facility did not call for evacuation, sheltering or other emergency steps.
The procedural path ahead is more familiar than the fire itself. The immediate emergency phase appears to have ended by Friday morning, but the investigation phase was just beginning. LyondellBasell said it could not determine the root cause before a full review. The Harris County Fire Marshal’s Office and local emergency agencies were involved during the response, and state environmental reporting requirements mean the company must finalize and submit more complete release estimates after the initial filing. That review is likely to focus on the sequence of the unit upset, the operation of pressure relief devices, the flare system and the point at which released material ignited. Investigators will also examine whether equipment, instrumentation, maintenance, procedures or operating conditions played a role. For the public, the next milestones are more concrete: updated release totals, any new environmental findings, and a fuller explanation from the company or regulators about what failed and why. Until then, the most basic questions remain open, including whether the event was triggered by a mechanical breakdown, a process imbalance, human error or a combination of factors.
At the scene and across nearby neighborhoods, the fire left a familiar mix of alarm and routine. Emergency managers told residents they might continue to notice response activity, even after the visible danger faded. Television crews returned Friday morning and still saw small flames inside the facility, though officials said the remaining fire was contained and not visible to the public from Bay Area Boulevard. Residents who posted images overnight described seeing a large glow and smoke over the plant, while officials kept repeating that no community action was needed. That contrast helped define the story. In public, the event looked dramatic and potentially dangerous. In official statements, it was increasingly described as controlled, contained and under investigation. Those two realities can exist at the same time in a petrochemical corridor where industrial incidents are highly visible and where communities often judge risk not only by air-monitoring data and official statements, but also by what they have seen before. The result by Friday night was a calmer scene, but not a settled one.
As of Friday night, the fire was out, no injuries had been reported and officials said air monitoring had not produced actionable readings. The next test for investigators and the company will be whether upcoming reports explain, in plain terms, what happened between the initial upset at 7:45 p.m. Thursday and the final containment of the fire early Friday.
Author note: Last updated March 14, 2026.