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 a person 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 present aboard the cargo ship Dali conducting court authorized law enforcement activity, the agency said in a statement Monday.

The investigation was first reported by The Washington Post.

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

The container ship 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 bodies from the underwater wreckage, while the remaining three victims are still unaccounted for.

National Transportation Safety Board Chair Jennifer Homendy said last week that investigators are focusing on the electrical power system of the massive container ship that veered off course. The ship experienced power issues moments before the crash, as evidenced in videos showing 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."

Monday's statement from Baltimore 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."

"We are continuing to do everything in our power to support everyone impacted here and will continue to recognize the human impact this event has had," Scott said in a statement. "Part of that work needs to be seeking recourse from those who may potentially be responsible, and with the ship's owner filing a petition to limit its liability mere days after the incident, we need to act equally as quickly to protect the City's interests."