The U.S. sued BP and eight other defendants on Wednesday over the Deepwater Horizon oil spill in the Gulf of Mex ico, seeking civil penalties under the Clean Water Act.

President Barack Obama's top Justice Department official, Attorney General Eric Holder, said both civil and criminal investigations continue into the April 21 spill, which spewed oil for months.

Hallibuton Inc - which was accused of shoddy construction work on the well ahead of the spill by some of the parties sued - was not charged.

We intend to prove that these defendants are responsible for government removal costs, economic losses, and environmental damages without limitation, Holder said.

Defendants include BP Exploration and Production, Inc., three Transocean companies, Anadarko Petroleum and its exploration arm, , MOEX Offshore, Triton Asset Leasing, and BP's insurer QBE Underwriting.

Alleged violations in the period leading up to the spill include failing to make sure the Macondo Well was kept under control, failing to properly monitor its conditions and maintain surveillance, and failing to maintain and use materials to ensure safety and protection of personnel, equipment, natural resources and the environment.

The department alleges in it complaint that those violations contributed to the spill and that defendants are responsible under the Oil Pollution Act.

The Clean Water Act violations alleged include breaking a prohibition of unauthorized discharge into the water.

The ongoing civil investigation is being handled by the Justice Deparment, the Environmental Protection Agency, the Coast Guard, the National Oceanic and Atmospheric Administration, and the Department of the Interior.

The company has promised to create a $20 billion claims fund over the next three years to pay for costs related to the spill and clean-up, as well as to compensate victims and businesses.