The insurer of the Baltimore bridge that was destroyed when it was hit by a container ship is reportedly preparing to pay $350m to the state of Maryland.

The Wall Street Journal reported that Chubb is expected to approve the sum within weeks, the first major payout since the 26 March disaster that left six construction workers dead and a likely multibillion-dollar bill for damages.

A criminal investigation is continuing after the 9,962-teu Dali (built 2015) hit a pillar of the Francis Scott Key Bridge. The body of a fifth construction worker inside a truck was recovered on Wednesday. The sixth worker remains unaccounted for.

The broker for the bridge’s insurance policy, WTW, confirmed the potential payout, according to the Wall Street Journal and Reuters.

It is likely to be the first of many payments related to the disaster. Damage to the bridge alone could exceed $1bn.

Baltimore’s mayor has filed legal papers claiming negligence by ship manager Synergy Marine and shipowner Grace Ocean, saying the Dali was unseaworthy when it left the port.

City officials alleged that alarms went off on the ship’s refrigerated containers before it left port, indicating an “inconsistent power supply” on the vessel.

Chubb is expected to support any action by the city authorities and families of the victims in the legal action. The shipowner and manager earlier went to court in an attempt to limit their liability for the accident.