PARIS (AP) _ A DC-10 airliner bound from the Congo to Paris with 170 people aboard disappeared on Tuesday, probably over the West African country of Niger, the French airline UTA said.

A U.S. ambassador's wife was among the passengers, and a Chadian Cabinet minister also was reported on board.

UTA said there was no sign of the plane's fate by nightfall, more than five hours after contact was lost.

Bonnie Pugh, wife of U.S. Ambassador to Chad Robert L. Pugh, was aboard, according to Robert Ayling, the deputy chief of mission, reached by telephone in N'Djamena, Chad. He said it appeared a full-scale search would have to wait until daylight Wednesday.

A State Department spokesperson in Washington, who spoke on condition of anonymity, confirmed Mrs. Pugh was aboard.

The French news agency Agence France-Presse, quoting unidentified sources, said Chadian Planning Minister Mahamat Soumahila was also aboard, bound for the annual meeting of the International Monetary Fund in Washington.

The report was not confirmed, and UTA did not immediately issue a passenger list.

UTA Flight 772, with 155 passengers and 15 crew, originated in the Congolese capital of Brazzaville and made a stopover in N'Djamena.

The airline said it believed the search focused on Niger, along the path the plane would have taken, and could involve military forces from Chad, Niger and France, which has a small force in Chad.

The last radio contact between the plane and air traffic controllers, 40 to 50 minutes after leaving the airport at N'Djamena, indicated everything was normal, the airline said.

UTA said that would be enough flight time to take the plane over the border into neighboring Niger. It reported no unusual weather in the area at the time.

The French navy dispatched a Dassault-Breguet Atlantique patrol aircraft from Dakar, Senegal, to join the search, the Defense Ministry said.

The Foreign Ministry formed a crisis team to maintain contact with the countries over which the plane could have flown, including Niger and Algeria, a ministry spokesman said, speaking on condition of anonymity.

The flight left N'Djamena at 1:13 p.m. (8:13 a.m. EDT) and should have arrived at Charles De Gaulle-Roissy International Airport at 7:15 p.m. (1:15 p.m. EDT).

UTA purchased the aircraft in 1973 and it logged 60,000 hours in the air. No indications of mechanical failure surfaced before the plane left Chad, UTA said.

Keith Takahashi, a spokesman for the Douglas Aircraft Co. in Long Beach, Calif., identified the aircraft as a DC-10-30, a popular model in the DC-10 series.

The disappearance came the same day the Federal Aviation Authority in Washington ordered a detailed inspection in the fan disks of all DC-10 engines.

An explosion in the tail engine of a United Airlines DC-10 on July 19 severed hydraulic lines operating the airplane's controls, forcing the pilots to make an emergency landing near Sioux City, Iowa, in which 112 people died.

Both FAA Administrator James B. Busey and National Transportation Safety Board Chairman James Kolstad declared the DC-10 to be safe.

A Korean Air Lines DC-10 crashed on landing July 27 at Tripoli, Libya, killing 78 passengers and four people on the ground.

Northern Chad was long the scene of battles between government forces and Libyan-backed rebels, but has been calm for two years. Chad and Libya have restored diplomatic relations and agreed to settle their territorial dispute at the border by peaceful means.