BEAUMONT, Texas (AP) — A Southeast Texas company and its ex-president have been charged with environmental violations that resulted in the deaths of two workers.

A federal grand jury's 13-count indictment was unsealed Wednesday, according to a statement from John Bales, the U.S. Attorney for the Eastern District of Texas. The grand jury has accused Port Arthur Chemical and Environmental Services, LLC and its former president, Matthew Lawrence Bowman, 41, of scheming to illegally transport hazardous materials without the proper documentation and placards.

Those actions led to the deaths of two truck drivers in December 2008 and April 2009, according to the statement. The truck drivers died of exposure to hydrogen sulfide, a toxic gas.

The conspiracy count carries a maximum sentence of five years in prison. The company can be fined up to $500,000.

The company produced and sold caustic materials to paper mills. Bowman and the company he owned and operated until November 2010 are accused of violating federal rules that regulate the transport of such hazardous materials.

The incidents are also being investigated by the U.S. Environmental Protection Agency, the Texas Commission of Environmental Quality and several other state and federal agencies.

The attorney general's office said it has no attorney listed for Bowman, who has not yet appeared before a judge.