"Stena Immaculate was on a short-term charter with Military Sealift Command," according to Jillian Morris, the spokesperson for the command, which operates civilian-crewed ships that provide ocean transport for the US Defense Department.

The tanker, which was carrying jet fuel, was at anchor about 10 miles (16 kilometers) off the eastern England port of Hull when it was "struck by the container ship Solong," according to Crowley Maritime, the US shipping firm managing the tanker.

The Stena Immaculate is one of three Crowley-operated and Stena-owned tankers -- along with the Stena Imperative and Stena Impeccable -- selected by the US Maritime Administration as part of a defense supply program.

The program was designed to guarantee that commercial vessels "can readily transport liquid fuel supplies in times of need for the US Department of Defense," Crowley said in a 2023 press release announcing its involvement in the defense fleet.

The tankers conduct international commercial voyages "but can be chartered on a short-term basis to serve the US government's operations," the release added.

A freight contract between Crowley and US Transportation Command was renewed for seven years in July 2024.

The contract, valued at $2.3 billion, is one of the US government's largest logistic contracts, according to Crowley.