The FBI is conducting a criminal investigation into the deadly collapse of Baltimore’s Francis Scott Key Bridge that is focused on the circumstances leading up to it and whether all federal laws were followed, according to someone familiar with the matter.

The person was not authorized to discuss details of the investigation publicly and spoke on the condition of anonymity to The Associated Press.

The FBI was aboard the cargo ship Dali conducting court-authorized law enforcement activity, the agency said in a statement Monday. It didn't elaborate and said it wouldn't comment further on the investigation, which was first reported by The Washington Post.

Meanwhile, Baltimore Mayor Brandon Scott on Monday announced a partnership with two law firms to “launch legal action to hold the wrongdoers responsible” and mitigate harm to city residents.

The massive Dali left Baltimore’s port in the early hours of March 26, laden with cargo and headed for Sri Lanka, when it struck one of the bridge’s supporting columns , causing the span to collapse into the Patapsco River and sending six members of a roadwork crew plunging to their deaths.

Divers have recovered three of the six bodies from the wreckage.

National Transportation Safety Board Chair Jennifer Homendy said last week that investigators were focusing on the ship's electrical power system . The ship experienced power issues moments before the crash, as is evident in videos that show its lights going out and coming back on.

Homendy said information gleaned from the vessel’s voyage data recorder is relatively basic, “so that information in the engine room will help us tremendously.”

In his statement announcing the partnership with law firms, Scott said the city “will take decisive action to hold responsible all entities accountable for the Key Bridge tragedy, including the owner, charterer, manager/operator, and the manufacturer of the M/V Dali, as well as any other potentially liable third parties.”

He said with the ship's owner already seeking to limit the company's liability , the city needs to act quickly to protect its own interests.

The investigation comes amid concerns about the safety of thousands of U.S. bridges and days after more than two dozen river barges broke loose and struck a closed span in Pittsburgh.