Swedish customs says it has boarded Russian ship in Swedish waters to conduct inspection

STOCKHOLM, Dec 21 (Reuters) - Sweden's customs service said on Sunday that authorities had boarded a Russian freighter that anchored in Swedish waters on Friday after developing engine problems, and was conducting an inspection of the cargo.

The owners of the vessel, the Adler, are on the European Union's sanctions list, Martin Hoglund, spokesman at the customs authority said.

"Shortly after 0100 last night we boarded the ship with support from the Swedish Coast Guard and the police service in order to make a customs inspection," Hoglund said. "The inspection is still ongoing."

Hoglund declined to say what the customs service had found on board the ship.

According to ship-tracking service Marine Traffic, the Adler is a 126-metre-long, roll-on, roll-off container carrier. It is anchored off Hoganas in southwest Sweden.

In addition to the Adler being on an EU sanctions list, the vessel and its owners M Leasing LLC are also both subject to U.S. sanctions, suspected of involvement in weapons transport, according to OpenSanctions, a database of sanctioned companies and individuals, persons of interest and government watchlists.

Hoglund said the ship had left the Russian port of St Petersburg on December 15, but he said customs did not have any information about its destination.

(Reporting by Simon JohnsonEditing by Frances Kerry)