Thousands of people fearing they were exposed to toxic benzene from a leak at a BP facility in Texas have filed a class-action lawsuit against the oil company.

The lawsuit, filed Tuesday, alleges the release of more than 500,000 pounds of chemicals -- including 17,000 pounds of benzene, a carcinogen -- jeopardized the health and property values of people who live and work in the area.

Two weeks before a well blowout in the Gulf of Mexico triggered the environmentally disastrous BP oil spill, the company had problems with a hydrogen compressor at its Texas City plant, scene of a 2005 explosion that killed 15 people.

The company said a fire April 6 compromised a seal on a hydrogen compressor, forcing BP to burn off gases. It reported the "emissions event" to the Texas Commission on Environmental Quality the following day. As it worked to fix the unit during the next 40 days, the plant released 538,000 pounds of pollutants into the air, BP told regulators.

Information about the release became public when BP submitted a final incident report to regulators in early June. The state commission cited BP for an "excessive release" and two weeks ago, it referred its findings to the state attorney general for possible litigation.