The U.S. Occupational Safety and Health Administration on Friday levied $236,500 in fines for safety violations found at Citgo Petroleum Corp's Corpus Christi, Texas, refinery following the six-month probe of a July explosion.

"Citgo did not ensure adequate maintenance and oversight of its process safety equipment, exposing workers to the release of toxic chemicals and posing a danger to not only the company's employees but to the community, as well," said Dean McDaniel, OSHA's regional administrator in Dallas, Texas.

Citgo has 15 days to appeal the fines, OSHA said.

Citgo confirmed receipt of the citation from OSHA on Friday.

"Citgo has received a citation and notification of penalty from OSHA," Citgo said in a statement. "Citgo will work with OSHA to resolve these issues.

OSHA's citation is the second time in two months federal safety investigators have said the alkylation unit blast, which severely injured one worker, almost released toxic chemicals into the air across Corpus Christi, which has a population of 300,000.

In December, the U.S. Chemical Safety Board's lead investigator called the blast a "significant near-miss."

"It was a significant near-miss of a hydrogen fluoride release into the refinery and into the community," said CSB Investigations Supervisor Robert Hall in December.

Hydrogen fluoride exposure can be fatal. It can cause damage to the skin, eyes, heart, lungs, and bones in humans.

The most serious of the charges against Citgo are two willful violations for failing to adequately repair and maintain process equipment.

In December, the CSB called on Citgo to audit operations at alkylation units at the 163,000 barrel per day (bpd) Corpus Christi refinery and the company's 167,000 bpd Lemont, Illinois, plant.

The board wants a third-party auditor to determine if alky unit operations at the two refineries conform with practices recommended by the American Petroleum Institute.

API issued the recommendations in 1992, saying such audits should be done every three years. Citgo has never done such an audit.

Hydrogen fluoride released in the explosion was prevented from reaching Corpus Christi by a water cannon system, which suffered several breakdowns, and prevailing winds blowing away from the city.

One worker, Gabriel Alvarado, was burned over 60 percent of his body in the blast and ensuing fire. He continues to recover from his injuries.

The CSB found 42,000 pounds of hydrogen fluoride was released in the fire. An estimated 4,000 pounds was not absorbed by the water spray from cannons.

The United Steelworkers union launched a campaign to ban alkylation units that use hydrogen fluoride following the Corpus Christi explosion. An alkylation unit makes octane-boosting additives for gasoline.

Citgo is indirect subsidiary of Venezuela's state-owned oil company PDVSA.