The massive fire overnight Tuesday at the ExxonMobil Refinery in Baton Rouge is suspected of releasing cancer-causing chemicals benzene and 1,3 butadiene, as well as other chemicals that are toxic at high enough concentrations, a Louisiana State Police report says.

But the amounts of those releases are unclear and likely will remain so for about a week, when ExxonMobil provides estimates to state regulators in what's known as a "seven-day" report.

State officials have said the blaze likely combusted many of those harmful chemicals, converting them into other materials — some of which are also toxic. Air monitoring inside, around and away from the plant did not detect harmful concentrations of chemicals being released into the air or among the broader public, according to state officials and public data. 

The initial incident report from State Police details ExxonMobil's response to the blaze, which took nearly seven hours to extinguish. The report shows brief updates over an 11-hour period from 11:58 p.m. Tuesday to 11:16 a.m. Wednesday, hours after the fire had been put out but while flaring was still underway.

ExxonMobil officials pointed out Thursday that the report, which is required by law no more than an hour after an emergency incident is discovered, captures early estimates from company officials as they are still trying to find out what is happening. They also inform firefighters, regulators and others about how they should help respond to the incident and protect the public.

The reports are written to err on the side of being more protective of public health, company officials said, adding estimates of chemical releases can change in later reports.

"We are very conservative. We tend to report early and often, and we can always retract it later," Robert Berg, ExxonMobil's state regulatory adviser, said Thursday.

Berg and company spokeswoman Stephanie Cargile emphasized that rigorous air monitoring shows the chemical release did not expose the broader community.

The first paragraph-long dispatch from ExxonMobil, as recounted by a state trooper, provides a sense of the battle with the raging fire by company officials and their internal firefighting force.

"We believe that we have a high potential of flammable vapor material being released," Exxon told police at the start of the incident. "We are currently working to contain the fire and will follow-up with an estimate once the fire is contained. The fire has not been secured at this time. Unknown release amount at this time. Fire visible from outside the facility."

The report says the fire had been discovered at 11 p.m. Tuesday. ExxonMobil didn't notify the State Police hotline until 58 minutes later, just under a one-hour deadline for emergency incidents. At the time, wind was recorded as blowing 8 mph from the northeast, the report says. 

The report says ExxonMobil's firefighters cut off a fuel line suspected of helping to keep the fire going, eventually gaining full control of the blaze.

"The fire was extinguished at 5:45 a.m.," the report says.

Other chemicals that ExxonMobil officials believe were released, according to the incident report, were unspecified "flammable vapor," crude oil and hydrogen sulfide. Company officials added in their dispatches to State Police that flaring necessitated by the "unit upset" from the fire had resulted in releases of sulfur dioxide that exceeded 500 pounds.

Flaring is when a facility intentionally burns material for safety or environmental reasons.

"Flammable vapor" is a term used in reporting hazardous incidents and encompasses a category of chemicals on a state list that could contribute to a fire, ExxonMobil officials said. Acknowledgement of that kind of vapor is meant to inform regulators about potential risk, but it wasn't immediately clear Thursday to what chemical the term referred in this instance.

The report does not indicate how much benzene was released from the fire and suggests that ExxonMobil officials were still trying to figure out that total in the first hours of the fire. 

The Advocate obtained the report Thursday from State Police through a public records request.

The fire inside the 2,100-acre refining, chemical and plastics complex off Scenic Highway did not cause any injuries. ExxonMobil also said the blaze did not hinder its ability to meet contractual commitments.

Citing anonymous sources, Reuters reported Thursday that the fire had cut production at the 502,500 barrel-per-day refinery and forced the shutdown of multiple units in the refinery and chemical operations.

The fire has prompted investigations by the state Department of Environmental Quality and by ExxonMobil to determine its cause. The U.S. Environmental Protection Agency has also been monitoring the fire and its aftermath, and the U.S. Occupational Safety and Health Administration has been on the scene.

Sources have told The Advocate and Reuters that the fire happened in the refinery's crude distillation unit, the rough starting point of the oil refining process.

Crude is fed into the unit and heated to temperatures surpassing 1,000 degrees Fahrenheit to allow impurities to come out and to break down the oil into different products as the temperature rises. They include lighter end products like butane and naphtha, mid-range products like kerosene and diesel, and heavier products like fuel oil, according to the U.S. Energy Information Administration.

The State Police report appears to hint further that the distillation unit was affected. One summary paragraph in the report appears to call it, erroneously, the "crude discolation unit."

ExxonMobil officials say they don't comment on the operational status of specific units. 

While benzene and 1,3 butadiene are known human carcinogens for long-term, chronic exposure, they are also highly flammable, according to materials safety data sheets and federal health websites.

The chemical 1,3 butadiene, in particular, is known to be extremely flammable and can pose a serious risk of fire and even explosion if accidentally released.

The State Police report indicates at least 10,000 pounds of the gaseous chemical were released. The gas, however, doesn't rise to the sky when released but is heavier than air and will linger along the ground, raising the danger of ignition.

Benzene is clear liquid at outside temperatures but is highly volatile, meaning it quickly evaporates into the air.

Several residents living near the plant reported hearing what they thought was an explosion from ExxonMobil, though Baton Rouge fire officials have said no explosion occurred. 


Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.