PORTSMOUTH, N.H. — The owners of the oil tanker that damaged a bridge connecting New Hampshire and Maine are asking a judge to dismiss a lawsuit filed by the two states seeking about $2.4 million in compensation.

The owners say costs to repair the Sarah Mildred Long Bridge, which reopened Monday, “constitute an improvement or betterment of the bridge” with new parts, so there should be a reduction in claimed damages. They also say the two states are “guilty of negligence to such a degree” that the states should be barred from recovering any damages, or recover a reduced amount.

The 473-foot tanker MV Harbour Feature struck the bridge on April 1 after breaking away from a pier.

The lawsuit, filed in U.S. district court in New Hampshire, alleged the incident happened because the crew “failed to property secure the vessel at her berth,” resulting the “parting of her mooring lines.”

Court records show the states asked a judge to order the “maritime arrest” of the tanker that would have allowed them to keep the ship in port. That seizure was avoided when the tanker owners posted a “special bond” for $2.4 million, the amount of the estimated repairs, on April 5.

The Portuguese tanker MV Harbour Feature is owned by Sexhste Nordtank-Hamburg and operated by TB Marine Shipmanagement.

Their attorneys deny that negligence by the crew led to the ship breaking away. They also said they do not have sufficient information to determine whether the accident caused “extensive physical damage.” The aging bridge has long been targeted for repairs, and is to be replaced by the end of the decade.