Families of Iraqis who died in a shooting involving Blackwater USA contractors in Baghdad have sued the company, saying the firm violated U.S. law and fostered a culture of lawlessness among its employees.

The suit filed Thursday in U.S. District Court in Washington, D.C., says the contractor has been paid more than $1 billion by the U.S. government since 2001 and that the company violated U.S. laws in the Sept. 16 killings.

"Blackwater has turned recklessness into profit at the expense of the lives of innocent civilians," said Vincent Warren, executive director of the Center for Constitutional Rights, which brought the suit. Warren made the comments in a brief interview after the suit was filed.

Seventeen Iraqis died in the Sept. 16 shootings.

Blackwater spokeswoman Anne Tyrrell said the company was aware of the lawsuit. "Because it is a matter currently under investigation by the FBI, we will refrain from commenting on the specifics of the case other than to say that the company will defend itself vigorously," she said.

The FBI arrived in Baghdad a week ago to investigate, taking over a State Department investigation and raising the prospect that it could be referred to the Justice Department for prosecution.

Blackwater protects U.S. diplomats as they move about on Baghdad's dangerous streets. An Iraqi investigation into the killings recommended that the State Department sever all contracts for the company's operations in Iraq within six months.

Blackwater should be liable for claims of assault and battery, wrongful death, intentional and negligent infliction of emotional distress, and negligent hiring, training and supervision, the lawsuit says.

The plaintiffs in the case are an injured survivor and three families of men who died in the incident.

The United States has not made conclusive findings about the shooting, though there are multiple investigations under way and Congress has opened inquiries into the role of private security contractors.

The Iraqi government report said its courts were the proper venue in which to bring charges.

Iraqi officials say Blackwater's license to operate in Iraq expired on June 2, 2006, meaning it had no immunity from prosecution under Iraqi laws set down after the fall of Saddam Hussein in 2003.

The State Department has counted 56 shooting incidents involving Blackwater guards in Iraq this year. All were being reviewed as part of the comprehensive inquiry ordered by Secretary of State Condoleezza Rice.