GONZALES — Louisiana State Police cited but did not fine Renewable Energy Group for a hydrogen gas explosion and fire in September at its Ascension Parish biodiesel plant that blew a worker off an I-beam and severely burned others.

The explosion was the second to occur at the Geismar facility in a five-month period in 2015. The company was not cited in the first incident.

A State Police report, completed last month, details the second explosion: a nighttime blast Sept. 3 that engulfed the workers in flames, leaving four people injured.

The document lays out the investigator’s decision to charge REG of Ames, Iowa, with the civil violation of careless handling of hazardous material, but it does not explain why State Police decided to cite the company with a violation, but not fine it.

State law says the careless handling charge can bring up to a $10,000 fine. REG’s penalty, however, was a warning letter issued Dec. 20, company officials said in a statement.

The State Police report, released after a public records request by The Advocate, found REG workers failed to take recommended safety steps to ensure hydrogen was no longer flowing from a storage tank into a high-pressure line that caught fire.

REG and Excel Group contractors were replacing gaskets in control valves inside the high-pressured line at the time of the explosion.

The highly flammable hydrogen gas, which is invisible and odorless, escaped, caught fire and exploded.

“I was knocked off the I-beam I was working on, and was suspended in the air, stuck in my harness,” wrote Mason Spratt, 23, in an account for investigators.

“I was engulfed in flames. My harness lanyard burned through and I was able to escape down the road to safety. Another REG employee extinguished the flames on my back.”

Among those burned was REG employee Nick Matassa, the son of Ascension Parish President Kenny Matassa.

The first explosion at REG occurred April 2 and was caused by a leaking solvent pump that had just been serviced. After an investigation, troopers decided not to cite the company with a violation.

When there is a new event, the State Police said they look at a plant’s history of explosions, fires or some other event, and such events are only counted if the company was cited with a violation, Lt. J.B. Slaton, State Police spokesman, said last week.

And then troopers would only count it as repeat offense if the second violation is identical to the first violation, Slaton said.

Since REG was not cited in the April explosion, the September explosion was considered its first offense.

Maj. Doug Cain, also a State Police spokesman, said companies can receive warnings if a violation is their first.

A violation will stay on a company’s record for three years. If the company is cited for the same violation within a three-year period, troopers treat the new violation as a second offense, Cain said.

Once the three-year period expires, however, similar violations would again be treated as first offenses.

“This case is consider closed,” Slaton said.

While the state has finished its investigations into the two fires at the plant, the U.S. Occupational Safety and Health Administration is continuing to investigate the April 2 and Sept. 3 incidents, said Juan Rodriguez, OSHA spokesman.

A company official said REG is working with OSHA in the investigation.

“The health and safety of our employees and providing a safe work environment is our top priority,” said Anthony Hulen, spokesman for REG. The State Police noted company officials and workers said they followed safety procedures, but investigators focused how those procedures were applied Sept. 3, according to the report.

A key valve — that would have closed off the flow of hydrogen into the line — was left open, an REG lawyer told State Police.

The investigator faulted REG for choosing this valve, which State Police said had no indicator that showed whether it was open, when there was another, safer two-valve method they could have used as the “lock-out point.”

A lock-out point is a spot where a valve is physically locked closed — often with a padlock — to isolate a line.

“Using this valve as a lock-out point failed to use the proper amount of caution needed for the scheduled repairs,” the investigator wrote in the report.

Narrative accounts contained in the report show workers noted, at some point, that the line was still under pressure, but from what they thought was nitrogen. Another crew had earlier used the nonflammable, inert gas to test the line.

Work was stopped so workers could double-check the line. All valves slated for repairs — not the lock-out valve — were partially opened to the atmosphere to see if pressure was in the line, workers told troopers.

Repair work resumed after workers gave the all clear, but, moments later, with hydrogen flowing out into the atmosphere, the fire ignited.

The investigating trooper said the company should have used another method to isolate the line, one in which two valves are closed and any lingering gas is allowed to slowly escape, or be bled off, to ensure the line has no pressure in it.

Troopers said such a location existed on the line.

Joe Wiley, general counsel for Excel Group, REG’s maintenance and construction contractor, agreed that the valve chosen to isolate the line was the wrong valve to select.

“The trooper’s findings are consistent with ours,” he said.

State Police did not cite Excel in the incident.

Follow David J. Mitchell on Twitter, @NewsieDave.