BP continued to operate its Texas City refinery after critical equipment broke down, illegally releasing 500,000 pounds of toxic air pollutants in April and May, the Texas attorney general contends in a lawsuit.

The state’s action follows an investigation that documented poor maintenance practices and multiple violations of the state’s Clean Air Act. The Texas Commission on Environmental Quality referred the case to the attorney general because the violations were “egregious,” John Sadlier, the agency’s deputy director of compliance and enforcement, told The Associated Press.

BP faces fines of up to $25,000 per day for each violation. The suit could also jeopardize BP’s probation for a federal conviction related to the massive 2005 explosion that killed 15 and injured 170 at the same refinery, The Houston Chronicle reports.

BP spokesman Scott Dean said Monday the company will continue to cooperate with state officials, but would not comment further on the pending litigation. Last week, The AP reported that Dean denied the allegations in the commission’s report.

The refinery, which is the third largest in the country, has been under heavy attack since the 2005 blast. In 2009, the Texas attorney general sued BP for 15 violations. The federal Occupational Safety and Health Administration also fined BP $87 million for workplace hazards that went uncorrected after the explosion.

According to the lawsuit, the plant began to emit toxic pollutants when a compressor malfunctioned and caught fire on April 6. Rather than shut down that part of the refinery while waiting for repairs, the complaint says, BP continued operations “so as not to reduce productivity,” allowing pollutants to escape for more than 40 days.

“BP made very little attempt to minimize the emission of air contaminants caused by its actions, once again prioritizing profits over environmental compliance,” the lawsuit states.

The environmental quality commission determined the company could have prevented the fire had it properly maintained the equipment.

BP also faces a $10 billion class action lawsuit on behalf of Texas City residents, who say they suffered health problems from refinery pollution.

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