BP announced yesterday it had reached a “significant milestone” by successfully plugging its ruptured well with heavy drilling mud, but the company’s troubles aren’t over yet. Separate from the lawsuits it faces over the Gulf disaster, BP’s now being sued by workers at its notorious Texas City refinery.

In two lawsuits filed in federal court in Galveston, workers at the refinery allege that BP’s recent toxic release—which, as we reported, occurred two weeks before the Deepwater Horizon blast and went on for 40 days—exposed them to dangerous chemicals that have since caused lingering health problems.

Both lawsuits accuse BP of acting with negligence. One seeks punitive damages of $10 billion. The workers allege that they’re “routinely” exposed to benzene, a carcinogenic constituent of petroleum that has also been detected in the Gulf.

“In order to avoid losing the profit from shutting down an operating unit, and in an attempt to avoid the publicity such a shutdown would have garnered in the financial press, the Defendant instead spewed thousands of pounds of one of the most deadly and nastiest carcinogens into the atmosphere, exposing unsuspecting onsite workers and nearby residents,” read one complaint, filed on behalf of 10 named plaintiffs and more than 2,200 others.The plaintiffs in this larger case are workers at the refinery and people who live or work in Texas City who also say they've been harmed by BP's chemical release.

That complaint also described an August 2009 incident in which a group of workers allegedly found chemicals spewing out of a broken pipe “like water from a fire hydrant.” They were taken to the hospital and later learned they had been exposed to benzene. According to the complaint, at least two more workers were sent to the hospital this past weekend due to another benzene exposure.

When I asked BP about the lawsuit's allegations, the company said it wouldn't be paying any claims related to the Texas City release.

"Based on our underderstanding of the facts and circumstances, BP does not believe there is any basis to pay claims in connection with this event," spokesman Scott Dean told me. During the 40-day release, "the community air monitoring network did not show elevated readings."

According to the Houston Chronicle, the lawsuits aren’t the only recent criticisms aimed at the company over safety concerns at Texas City. Survivors of a 2005 blast at the refinery—which killed 15 workers—say recent events in the Gulf and at the Texas City plant prove the company cannot be trusted; they’re calling on the Justice Department to revoke the terms of BP’s 2007 plea deal for the fatal 2005 accident.