RIO DE JANEIRO, Wednesday, July 18 — An Airbus 320 with at least 176 people on board skidded off a runway while landing Tuesday night at the main airport in São Paulo, Brazil’s largest city, and crashed into an office building and a gas station across a highway, setting off a conflagration that took firefighters more than six hours to bring under control.

Brazil Plane Crash

The governor of the state of São Paulo, José Serra, who was at the scene, said that the chances of passengers and the crew having survived the crash and ensuing explosion that broke the airplane into at least two pieces were almost zero, according to the Web site of the local newspaper, Folha de São Paulo.

Brazilian cable television showed firemen carrying body bags away from the site, and Mr. Serra said there were also fatalities on the ground. The flight, number JJ 3054 operated by the privately-owned TAM Airlines, was arriving from the southern city of Porto Alegre when the accident occurred just before 7 p.m.

If Mr. Serra’s assessment proves true, the crash would be the worst in Brazilian history. Just after midnight, state police officials told reporters that 40 people were confirmed dead, but added that it could not yet be determined whether those victims were passengers on the plane, pedestrians on the street, employees in the building or motorists on the highway just past the raised runway. The building and gas station sit across the highway from the airport. Early reports indicated the plane flew over the road before crashing.

Initial estimates put the number of people on board the plane at 176, but The Associated Press news agency reported later today that the airline had raised the number by four to 180. A public safety official said that 15 of the bodies recovered so far were of people on the ground, The A.P. reported.

Civil aviation in Brazil has been in crisis since last September, when the nation’s worst airline disaster, a collision over the Amazon between a passenger plane and a business jet, took place. Since that disaster, in which 154 people were killed, Brazil, Latin America’s most populous country, has been racked by waves of canceled flights, air controller strikes and go-slow actions, struggles between military and civilian officials for control of the government’s aviation regulatory agencies and disclosures that the national radar system is deficient.

The accident on Tuesday occurred at Congonhas Airport, which is Brazil’s busiest and serves domestic flights. More than other Brazilian airports, Congonhas has suffered repeated flight delays and cancellations in recent months, in part a result of a renovation and modernization of the main runway that was meant to reduce the risk of airplanes losing their grip on the worn concrete landing surface.

That project was mainly finished late last month, but airlines have complained that the problem persists, and on Monday a commuter plane skidded along the runway before the pilot regained control. Tuesday was a day of persistent rain in São Paulo, and engineers and physicists who spoke on Brazilian television Tuesday night suggested that those conditions contributed to the TAM pilot’s losing control of his aircraft.

“It was to be expected this would happen,” Carlos Camacho, security director of the National Union of Airline Employees, told the Web site of the newspaper O Estado de São Paulo just hours after the crash. “A full-up plane, heavy, on a rainy day, with water pooling, and the pilot ends up not having control of the airplane.”

In February, a federal judge prohibited large planes, including Airbuses, from landing at or taking off from Congonhas, arguing that conditions were not safe. But the ruling was quickly overturned by a higher court, which argued that the measure was too drastic and would have a negative economic impact.

“From the start, we have maintained that the airport should remain closed so long as the renovations are not concluded” properly, Mr. Camacho said. “But nobody wants to lose; nobody wants to give up power or profits.”

But Mr. Serra and air safety experts said it was too early to be guessing about the causes of the accident. They suggested that other factors could be involved, ranging from defective brakes to problems with the hydraulic system, and urged Brazilians, whose fear of air travel is sure to increase as a result of the second tragedy in less than a year, to await the results of the official investigation that is already under way.

The plane appeared to have crashed head-on into a four-story building that is owned by TAM, Brazil’s largest airline, and is used for cargo shipments. City authorities ordered all available municipal firefighters to report for duty, and a score of ambulances could be seen in the area around the airport waiting for the fire to be brought under control.

Although at least part of the plane appeared to hit the gas station, Mr. Serra told reporters at the site that “it’s almost a miracle” that the plane did not hit it directly. If it had, he said, “we would have had a tragedy of much greater dimensions.”

He said federal aviation authorities told him the pilot apparently realized that he was not going to be able to regain control of his aircraft before the runway ended and “made an attempt to take off again.”