U.S. prosecutors are preparing what would be the first criminal charges against BP Plc staff after the worst U.S. oil spill last year, the Wall Street Journal reported, citing unidentified people familiar with the matter.

Prosecutors are focusing on whether some BP employees, including several Houston-based engineers and at least one supervisor, provided false information to regulators about the risks linked to the drilling of the Macondo well in the Gulf of Mexico, the Journal said.

Scott Dean, a spokesman for BP in Chicago, and David Nicholas, a London-based spokesman for the company, declined to comment on the report.

The April 2010 Macondo well blowout and ensuing explosion killed 11 workers on the Deepwater Horizon rig.

The accident led to hundreds of lawsuits against London-based BP, and the company spent $17.7 billion last year on its response to the spill and set up a $20 billion compensation fund for victims.

The charges may be brought early next year, with a conviction carrying a penalty of five years in prison, according to the report.

The U.S. Department of Justice may still decide not to bring charges against BP’s employees, the Journal said, citing the unidentified people.

BP faces at least 350 lawsuits by thousands of coastal property owners and businesses claiming damages from the more than 4.1 million barrels of oil that gushed from its well off the Louisiana coast.