ANCON, Peru (AP) _ A Peruvian jetliner carrying 70 people _ including four Americans _ crashed into the Pacific Ocean early today after the pilot reported his navigational system had failed. There were no signs of survivors.

Navy patrol boats found the wreckage of the plane 40 miles west of the town of Ancon this morning, said Adm. Jaime Monge, head of navy rescue operations.

The plane's fuselage had split in half. Heavy fog was hampering efforts to locate anyone who might be alive in the frigid waters, he said.

The body of a male passenger had been recovered, Lima's Radioprogramas radio station reported from an air force plane over the wreckage. There was no immediate confirmation from Peruvian authorities.

Airline officials said most of the passengers were from Latin American countries, including 30 Chileans. Among the rest were were four Americans, two British citizens, two Italians and one passenger each from New Zealand and Spain.

The National Transportation Safety Board offered its laboratories and other technical support to help the Peruvian government investigate the crash.

Aeroperu Flight 603 had flown from Miami to Lima and was en route to Santiago, Chile, when the pilot of the Boeing 757 said he no longer knew where he was.

``What's happening? What altitude am I at? Why is my ground crash alarm on? Am I over land or sea?'' the pilot said, according to Transportation Minister Elsa Carrera.

Raul Chiappo, Miami operations manager for Aeroperu, said the plane carried 20 passengers who began their trip in Miami and one who boarded there after flying in from John F. Kennedy airport in New York. Their nationalities were not immediately known.

The plane left Lima at 12:42 a.m. today and the pilot reported mechanical failure five minutes later, asking to return to Lima, the airline statement said.

The transportation minister said the tower told the pilot, Erick Schreiber, that he was over the ocean, and he then asked for a plane to guide him home to the airport. He was told a guide plane would arrive in 15 minutes.

The tower lost contact with the plane at 1:10 a.m.

The plane carried 61 passengers and nine crew members, the airline said, although the 757 has a 180-person capacity.

Armando Vicente, airport manager in Lima, said the aircraft was not the same plane that left Miami. Both the plane and crew were changed in Lima, but the flight number remained the same, he said.

Jesus Herrera, a fisherman who lives in a wooden shack 40 feet from shore near Ancon, said he heard a rumble during the night. Ten minutes later, his shack was flooded with a surge of water.

Navy and fire department boats were searching the area today and planned to drop inflatable rafts down to any survivors, said fire chief Gen. Juan Piperes of the Lima port of Callao.

``They have seen the plane's lights floating on the sea,'' Callao fire department dispatcher Zoraida Reyes said before dawn.

Officials had lined up ambulances, fire trucks, gasoline-powered generators and reflectors on the dark beach before dawn so any survivors could swim toward the bright lights.

However, it was not likely that survivors could last for long in the cold waters of the Humboldt current that flows up the South American coast from Antarctica.

At Miami International Airport, the flight schedule board at the unstaffed Aeroperu counter showed that Flight 603 began in Miami and departed at 6:30 p.m. Tuesday with stops in Lima, Peru; Santiago, Chile; Sao Paulo and Rio De Janeiro, Brazil; and Buenos Aires, Argentina.

Aeroperu was owned by the Peruvian government until it was purchased by Aerovias de Mexico three years. Its operations continue to be based in Lima, Peru.

A commercial jet crashed in southern Peru in February, killing 123 people. The government attributed the crash of the Faucett Airlines Boeing 737 to crew error.

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Aeroperu has set up a phone number for family members seeking information about passengers on Flight 603: (305) 448-1454, ext. 4.