Charles Dean went missing in 1974

One of the four is thought to be the brother of the American presidential contender, Howard Dean.

Charles Dean disappeared while travelling along the Mekong River as a tourist in 1974.

The remains were found with some of his possessions earlier this month in a rice field in central Laos.

As well as Dean they are thought to include his Australian travelling companion, Neil Sharman.

The other two bodies are believed to be US soldiers who went missing during the Vietnam War.

"Today marks another special day for the repatriation of remains from the Indochina War," the US Ambassador to Laos, Douglas Hartwick, said at the repatriation ceremony.

Forensic

Lao and Australian officials also attended the event at Vientiane's international airport, where caskets containing the remains of the men were draped with their countries' flags, before being loaded on a plane bound for Hawaii.

Howard Dean is the frontrunner in the Democratic presidential race

There they will undergo forensic testing to confirm their identities, a process which could take months.

Charles Dean and Neil Sharman were travelling around the region when they went missing 29 years ago during the Vietnam War.

It is thought they were held prisoner by Lao Communist guerrillas on suspicion of being spies, before they were executed.

Howard Dean has acknowledged that there has been speculation that his brother worked for the CIA, but he said he did not believe it.

On hearing last week that the remains were likely to be those of his brother, Mr Dean said: "This is a very emotional day for the Dean family. We greet this news with mixed emotions, but we're gratified and grateful that we're now approaching closure"

A sock, some shoes and a bracelet were found near the burial site. Mr Dean has said he is certain they belonged to his brother.