(Updates with new information)CARACAS, Jan 4 (Reuters) - A plane carrying 14 people, including eight Italians and one Swiss passenger, crashed into the sea close to a group of Venezuelan islands on Friday and had not yet been found, officials said.Air rescue and civil protection officials said rescue workers in speed boats and helicopters were still searching for the twin-engine aircraft nearly 10 hours after it went down.The officials said the pilot reported engine problems just before contact was lost with the Czech-made 19-seat LET L-410.The plane was flying to the Los Roques archipelago from Caracas but reported engine trouble and never arrived at its destination, an air rescue worker said.Rain and strong waves have "made the search for the plane more difficult," Gen. Antonio Rivero, who heads Venezuela's civil protection agency, said in an interview with a local television network.Rivero said earlier that four additional passengers boarded the plane at the last minute, taking the total to 18 on board, but civil protection said later that information was incorrect.A spokesman at the Italian Foreign Ministry said eight of the people on board the plane were Italians. He gave no further details.Civil protection said the plane, operated by Venezuela-based airline Transaven, fell into the sea about 24 miles (39 km) from Los Roques on Friday morning. The agency said in an evening press release that one of the passengers on board was Swiss, after having earlier identified that passenger as American.The nonprofit Aviation Safety Network reported on its Web site that in 2005 a Transaven-operated aircraft made an emergency landing after taking off from Caracas for Los Roques.In 2002, another Transaven plane made an emergency landing in the sea while flying to the same islands, according to Venezuelan media. Thirteen people on board were uninjured.Los Roques is a national park off the coast of Venezuela, renowned for white sand beaches and crystalline water popular with European and U.S. tourists. (Reporting by Frank Jack Daniel and Brian Ellsworth; Editing by Peter Cooney)
A file photo of a Russian Let L-410MU, an earlier version somewhat comparable to the one involved.
An aircraft owned and operated by Transaven Airlines is believed to have crashed into the sea off the coast of Venezuela. 14 or 18 people were on board.

The dual-engined Czechoslovakian-built (in 1987) Let L-410UVP-E3 plane had departed from Simon Bolivar International Airport near Caracas on its scheduled domestic flight to Los Roques Airport and is believed to have subsequently crashed into the ocean approximately 24 miles (39 km) short of its destination in the Los Roques archipelago, according to General Antonio Rivero, emergency management director for Venezuela. Initially, ''Bloomberg'' and ''Aviation Safety Network'' had reported that the plane had left the airport at Los Roques on its way to Caracas prior to the accident.

''Reuters'' reported that the crash was initially noticed when the plane failed to arrive at the Los Roques, according to air rescue worker Caleb Castro. Rivero told ''Reuters'' that four extra passengers had boarded at the last minute, bringing the total on board to 18.

The Italian foreign ministry told reporters that eight of those on board were Italian, whilst Rivero's agency said the others were five Venezuelans and an American. The United States embassy said it had no information about details of their citizen on the flight, and a subsequent release said it was possible he or she was in fact Swiss.

Search and rescue teams are using a navy frigate and patrol boats and helicopters to search for any survivors. "Speed boats, a plane and a helicopter are searching for the aircraft," Castro said to reporters.
A NASA satellite image of Los Roques archipelago
Luis Diaz, operations director for civil protection, said that the plane had reported engine trouble shortly before contact was lost. Although weather is not presently considered a factor, as conditions were good at the time, rains and high waves have developed and are hampering search efforts. Transaven have had two previous incidents, but no accidents. In 2002 a Transaven plane performed an emergency landing on water, in which all thirteen on board escaped uninjured. The other was a standard emergency landing in 2005. Both were on the same Caracas-Los Roques route.

Transaven, a small local company, regularly flies to Los Roques, a national park and a popular tourist destination boasting white sand beaches and world-class scuba-diving sites.