Editors note: This story has been updated with comments from Toby Baker, executive director of the Texas Commission on Environmental Quality, the U.S. Environmental Protection Agency and industry attorney Trey Overdyke.

The Port Neches chemical plant where two explosions and an ongoing fire prompted widespread mandatory evacuations Wednesday has a years-long history of state and federal environmental violations.

The facility owned by Houston-based Texas Petroleum Chemicals, or TPC Group, which manufactures highly flammable 1,3 butadiene and other petrochemicals, has been fined by the Texas Commission on Environmental Quality (TCEQ) and U.S. Environmental Protection Agency (EPA) more than half a dozen times in the past five years after the agencies found some of the facility's air pollution emissions avoidable.

State data shows the facility has reported spewing more air pollution than allowed by its government-issued permits about 70 times in the past decade and six times this year. That includes the most recent incident, in which it estimates that 1,000 pounds of butadiene and 500 pounds of particulate matter was released.

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Though the exact cause of the fire and explosions, which injured several workers and residents, is still unknown, local emergency response officials said it had been traced to a processing unit that held butadiene, a colorless gas used to make rubber and plastics that is a known human carcinogen. The first explosion took place around 1 a.m. The second occurred Wednesday afternoon, prompting mandatory evacuations within a 4-mile radius of the plant in Port Neches, Groves, Nederland and northern Port Arthur.

Online records show TCEQ has penalized TPC Group's Port Neches facility at least 18 times in the past decade, including three times this year. Most of the penalties are for air pollution events the agency found to be avoidable. The last federal censure TPC faced was in 2017 when it was ordered under a consent decree to pay a civil penalty of $72,187, make various equipment upgrades and spend no less than $275,000 on fenceline monitoring for butadiene.

At the time of the explosions, EPA's enforcement history website indicated the facility had been considered a high priority violator of federal clean air laws for more than two years. But on Dec. 6, nine days after the incident began, an agency spokesman said in a statement that its enforcement history website was incorrect and it was working with TCEQ to update it.

"EPA confirmed with TCEQ that they do not have any unaddressed Clean Air Act High Priority Violations involving the TPC facility," the statement said. "EPA is working with the Texas Commission on Environmental Quality (TCEQ) to correct this data issue."

Trey Overdyke, a Wyoming-based attorney who has represented companies after similar industrial incidents, said it's not surprising that the TPC facility has a record of environmental violations — but not because it's a bad actor.

"This is a highly regulated industry," he said. "In highly regulated industries, it is not uncommon for a facility to have some sort of enforcement history."

But environmental groups see repeat violations as a sign of lax environmental enforcement. Shortly after the explosions, they said that penalties TPC has faced — the civil ones add up to less than $200,000 — are nowhere near enough to deter a company that brings in billions of dollars a year from taking sufficient corrective actions.

“When you look at all these facilities and their compliance histories, it’s like a rap sheet,” said Elena Craft, senior director for climate and health at the Environmental Defense Fund. “And of course we see many times these bad actors that continue to have violations and ultimately this can lead to the kind of major disasters like the explosion last night.”

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There have been multiple, major fires and explosions at Texas chemical plants in recent years that have resulted in injuries and deaths, particularly in the Houston area. Like with Port Neches, many of the facilities had long histories of repeat violations.

In a statement issued Wednesday, TCEQ Executive Director Toby Baker called the string of incidents "unacceptable."

"Within the last year, I have witnessed an unacceptable trend of significant incidents impacting the Gulf Coast region," he said. "While not all emergency events may be prevented, it is imperative that industry be accountable and held to the highest standard of compliance to ensure the safety of the state’s citizens and the protection of the environment."

But a 2017 investigation by The Texas Tribune found that the TCEQ, which is responsible for administering federal clean air laws, fined fewer than 1% of so-called "emissions events" — when a facility emits more air pollution than is allowed by its permits — in 2016. While most of the releases don't pose imminent threat of fire or explosion, some do.

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When the TCEQ did fine companies, those penalties often make up a sliver of revenues and profits — even when the emissions events were potentially catastrophic — and the commission often waives a portion of them if the companies agree to address the underlying issue in a timely manner.

The three fines TCEQ handed down to TPC Group this year were for $50, $13,688 and $7,500, but the agency agreed to defer one-third of the amount.

In an incident update posted to its website Wednesday morning, TPC, which celebrated its 75th birthday this year, said it “sincerely remains focused on protecting the safety of responders and the public and minimizing any impact to the environment.”

In a written statement, Catherine Fraser of Environment Texas said, “Disasters like these are terrifying and unacceptable, and the TCEQ and EPA need to take much tougher enforcement actions and strengthen safety regulations, like the Chemical Disaster Rule, to build safer and healthier communities.”

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The Port Neches incident comes a week after the EPA gutted the so-called Chemical Disaster Rule — safety regulations enacted by the Obama administration that strengthened a decades-old EPA program designed to prevent and mitigate chemical disasters.

The rule would have required companies to study ways to avoid incidents by using better technology, engage in regular planning session with first responders, provide more information to first responders and the public about what types of chemicals they store on site — and to do third-party audits and root-cause analyses after incidents or near misses.

As authorities investigate the cause of Wednesday's explosions, it’s difficult to say whether the Port Neches incident could have been prevented if the rule had been in effect. But Heather McTeer Toney, who was a regional administrator for the EPA under the Obama administration, said, “what we can say with all certainty is that rules like this are critical to ensuring that we’re at least aware and are doing everything that we can to prevent these types of explosions.”