FREETOWN (AFP) -- Sierra Leone has launched an investigation into a helicopter crash that killed 22 people on board, most of them Togolese sporting officials and fans, government officials said on Monday.

A Russian co-pilot was the only survivor of the crash of the Russian-made Mi-8 Paramount Airlines helicopter, which exploded and caught fire while coming in to the country's main Lungi airport late Sunday and crash-landing on the runway.

Denis Ivanov, the privately-owned airline's managing director, said 20 passengers plus two Russian crew -- a pilot and a flight engineer -- were killed in the accident.

Sierra Leone Vice-President Solomon Berewa's office said a team of experts has been set up to investigate the cause of the crash. Transport Minister Prince Harding earlier appealed "for international support to get it (the probe) under way." ---------National mourning

The Togolese government on Monday declared three days of national mourning for the victims, and said it had sent a delegation to Freetown to inquire into the circumstances surrounding the accident.

It also dispatched a relief plane to airlift its national football team, who were stranded in Freetown after the crash also claimed the lives of the pilots of a charter flight they used for the trip from Lome, according to a Sierra Leone government director of sports, Saidu Mansaray.

All commercial helicopter flights have been "suspended with immediate effect" said government.

Ivanov, whose company is on the European Union blacklist of airlines which bars it from EU airspace, said a technical fault was unlikely to have been the cause of the accident.

"I was told there was an explosion on board from the passenger cabin just as the helicopter was coming to land. So I think we can rule out any technical problem for now," he said.

Togo's Sports Minister Richard Attipoe and 19 other people, mainly sporting officials and football supporters, were aboard the helicopter taking them to the airport across the Sierra Leone river estuary from Freetown.

The bodies were taken early Monday from Lungi to a government hospital in Freetown, and were expected to be transported home to Togo later in the day, according to Mansaray. Chernor Ojuku Sesay, spokesman for the Sierra Leone Football Association which hosted the Togolese, said that "most of the victims were burnt beyond recognition."

The victims were using the helicopter to return to the airport after attending the match in which the Togo national football team beat Sierra Leone 1-0 in an African Cup of Nations elimination match.

Paramount Airlines operates four blue, white and yellow helicopters which offer a seven-minute shuttle service between Freetown and the airport.

Alternative routes to the airport are either a 30-minute ferry ride or 110 kilometers (70 miles) by rough road.

The Togolese team was in Freetown awaiting the next shuttle when the accident took place.