The river was closed near Greenwich Pier after the tug “Chieftain” capsized while towing a barge, a spokesman for the Port of London Authority said.

Three crewmembers were believed to have been on board and two had been rescued.

“Regrettably a third crew member is missing in the water. We have a major search and rescue under way to try to locate him,” the spokesman said.

The tug capsized shortly before 11 a.m. (1000 GMT).