HOUSTON -- BP Products North America Inc. is being sued by Texas authorities who accuse the petrochemical giant of 46 pollution violations at its Texas City refinery -- including one tied to an explosion that killed 15 workers and injured 170 others four years ago.

The suit filed by the Texas Attorney General's Office in state court in Austin last month and announced Thursday alleges the BP Texas City refinery, about 35 miles southeast of Houston, spewed hundreds of thousands of pounds of pollutants in a "pattern of unnecessary and unlawful emissions."

The state said the emissions were the result of poor operational practices and inadequate maintenance at the refinery, the nation's third largest, refining 460,000 barrels of crude oil daily.

"BP Products is charged with polluting our environment, concealing information from authorities and harming Texans," Attorney General Greg Abbott said in a statement. "In recent years, more than 45 unlawful pollutant emissions occurred at BP's Texas City facility.

"This enforcement action holds BP accountable for failing to comply with environmental, health and safety laws that are intended to protect Texans from harm," he said.

According to the suit, which court documents indicated was filed May 22, among the improperly released air pollutants were volatile organic compounds, carbon monoxide, hydrogen sulfide, sulfur dioxide and nitrogen oxides.

"We have no comment on this pending litigation. Our goal is to resolve this matter and address the state's concerns. We are working hard to reduce the number of emissions events at the Texas City refinery. We have made substantial investments (more than $1 billion) in our people, in our work processes and in upgrading our facilities. When they fully take hold, the improvements we are making should deliver a significant decrease in the number, size and frequency of emissions events at the refinery," said Daren Beaudo, a press officer with BP America.

The suit seeks an injunction requiring BP to take all necessary steps to eliminate future unlawful emissions. The state also wants BP to install additional air-quality monitors "to ensure future compliance with emissions restrictions" and is seeking unspecified civil penalties, fines and attorneys' fees.

A hearing on the state's request for a temporary injunction is scheduled for June 29 in Austin.

Abbott said the Texas Commission on Environmental Quality filed 15 enforcement orders against BP between 2000 and 2007. He said the company was required to report unlawful emissions to the state environmental agency and fix the problems. BP, however, not only failed to comply with time deadlines to report the emissions to state authorities but also failed to take steps to prevent additional illegal emissions in a timely manner, Abbott said.

The fatal explosion in March 2005 led to an unlawful release of contaminants for more than 160 hours, Abbott said. The TCEQ later determined the event was "avoidable" and was the result of BP's "poor operations practices."

In March of this year, a federal judge in Houston approved a plea deal, highly criticized by victims, that fined parent British oil company BP PLC $50 million for its criminal role in the blast. The agreement included BP's subsidiary pleading guilty to a violation of the Clean Air Act, a felony, and also placed the company on three years probation.

A month earlier, BP agreed to pay almost $180 million to settle a federal pollution case with the Department of Justice and Environmental Protection Agency. That agreement, which federal authorities said addressed BP's failure to comply with a 2001 consent decree, included spending $161 million on pollution controls, $12 million in penalties and $6 million to reduce air pollution near the Texas City refinery.

About 1,100 employees and 2,200 contract workers were at the site when the 2005 explosion occurred at the 1,200-acre plant near Houston.

The plant processed 433,000 barrels of crude oil a day and 3 percent of the nation's gasoline.