The owner and manager of the ship that hit a Baltimore bridge, destroying the structure and leaving up to six dead, have filed papers in court to limit their liability — a move that will trigger the legal battle over the casualty.

Grace Ocean and Synergy Marine lodged a petition in a federal court in Baltimore to cap legal exposure at nearly $43.7m — although the figure is a provisional estimate that the companies’ lawyers plan to update.

The amount pales in comparison to an estimate by Barclays analysts that overall claims could reach $3bn.

Singapore-based Grace Ocean is the owner of the 9,962-teu Dali (built 2015), which slammed into the Francis Scott Key Bridge last week, leading to the structure’s collapse. Synergy, also of Singapore, is the technical manager.

After the incident, two construction workers are confirmed dead, and four are missing, presumed dead. Two others were injured.

In court papers filed on Monday, the two companies provided insight into their view of the facts leading up to the incident and denied they were to blame.

They said that seven to 10 minutes after the second of two tugs cast off from the Dali in the early hours of 26 March, the container ship suffered a loss of power and propulsion in the Patapsco River as it departed Baltimore for Sri Lanka.

The Dali was able to regain power briefly before losing it a second time.

“The vessel drifted to starboard, then dropped anchor in response to the loss of power and propulsion,” the companies’ lawyers wrote.

The ship then suffered an allision — a legal term for a collision with a fixed object — with the bridge.

“The casualty was not due to any fault, neglect or want of care on the part of petitioners, the vessel, or any persons or entities for whose acts petitioners may be responsible,” the lawyers wrote.

A limitation-of-liability filing was widely expected, as shipowners often use such litigation to corral a multitude of claims in one case.

Under long-standing law shielding shipowners from facing the full brunt liability of maritime casualties, lawyers came to the provisional calculation through a formula based on the post-casualty value of the ship plus freight.

Grace Ocean and Synergy estimate the ship was worth $90m, that repairs could cost $28m and that salvage expenses are estimated at $19.5m.

Also factored into the limitation-of-liability request is $1.17m in pending freight.

The petition was filed by lawyers from US firms Duane Morris, Blank Rome and Seward & Kissel.