Rescuers were looking for more than two dozen crew of a ship that broke into two during a typhoon in the South China Sea on Saturday.
The 30-strong crew of the engineering vessel abandoned ship when it “suffered substantial damage and broke into two pieces” about 160 nautical miles south-west of Hong Kong, according to the Hong Kong Government Flying Service.
Three people had been rescued as of 3pm local time [0700 GMT] and were taken to hospital for treatment, authorities said.
Video from Hong Kong authorities showed a person being airlifted on to a helicopter while waves crashed over the deck of the semi-submerged ship below.
The three survivors said other crew members may have been swept away by waves before the first helicopter arrived, according to a government statement.
Typhoon Chaba formed in the central part of the South China Sea and, on Saturday afternoon, made landfall in Guangdong province in southern China.
Rescuers in Hong Kong were notified of the incident at 7.25am local time and found the ship near Chaba's centre, where harsh weather and nearby wind farms made the operation “more difficult and dangerous”.
Wind speeds of 144 kilometres an hour and 10-metres high waves were reported around the ship's location authorities said.
The Government Flying Service sent two sorties of fixed-wing aircraft and four helicopter sorties, with mainland Chinese authorities sending a rescue ship.
Rescuers said they would increase the search area “due to the large number of people missing” and extend the operation into the night if conditions allowed.