Edinburgh, Aug 24 (IANS): Four people were killed after a helicopter with 18 people on board ditched in the sea off Shetland, northeast of the British mainland, police said Saturday.

The other people have been rescued, according to the reports, adding that those on board the helicopter included 16 workers and two crew, Xinhua reported.

The incident happened two miles (3.22 km) west of Sumburgh airport at 6.20 p.m. Friday as the helicopter was transporting people from oil and gas platforms in the North Sea back to Shetland, reported the Sky TV news.

"The bodies of three people have been recovered and work is underway to recover the body of the fourth person," Scotland police said in a statement.

A total of 14 people were rescued from the sea, including the two crew members in a search operation involving coastguard, police, the United Kingdom's Royal Air Force and local lifeboats, said the report.

Five people were discharged from hospital and nine detained overnight for observation, added the police statement.

The helicopter lost communication as it approached the airport on the southern tip of Shetland, said the Helicopter operator company.

Scottish First Minister Alex Salmond expressed sympathies with the families, friends and colleagues of those who lost their lives in this tragic incident, expecting the result of a full investigation by the relevant authorities.