One of the two thrust reversers on an airliner carrying 186 people that crashed in a fireball was turned off when the plane landed, the jet's owner said, as officials tried to determine why it raced down a runway instead of slowing down.

The airline TAM, however, said late Thursday that the thrust reverser used to slow jets after they touch down had been deactivated earlier in accordance with proper procedures and planes in such condition are considered safe to fly.

Brazil's Globo TV reported that an unidentified problem in the Airbus 320's right thrust reverser emerged four days before the crash and was under investigation by authorities.

TAM did not provide details about the problem, but issued a statement saying that government-approved maintenance rules allow planes with that problem to fly, though they must be inspected within 10 days.

The crash Tuesday night killed least 190 people: all 186 aboard the TAM Linhas Aereas SA jet and at least four on the ground, including one who died in a hospital Friday.

President Luiz Inacio Lula da Silva is expected to address Brazil's deadliest air tragedy in a televised speech Friday night. His administration has come under fire for failing to deal with the nation's glaring air travel safety problems despite obvious warnings, but his only comment since the plane crashed Tuesday night was a brief statement of condolences.

"Where is the president who loves to give speeches?" political commentator Lucia Hippolito asked.

One of Silva's top aides came under heavy criticism Friday after he was captured on video by Globo TV using an obscene gesture in apparent relief while watching the network's report about the thrust reverser.

Brazilian media and opposition politicians condemned Marco Aurelio Garcia, saying he appeared pleased that the report indicated a mechanical problem may have caused the crash because that would shift blame away from the government.

Garcia denied the claim and complained that the nation's biggest television network filmed him without his knowledge through his office window in the presidential palace in Brasilia.

Meanwhile, authorities struggled to determine why the TAM jet did not slow down after landing. Airport video showed TAM Flight 3054 from Porto Alegre speeding on the rain-slicked tarmac more than four times as fast as planes landing around the same time, raising the possibility of pilot or mechanical error.

The Airbus 320 then appeared to take off again and flew just above cars in rush hour traffic before slamming into a building.

Brig. Jose Carlos Pereira, president of the national airport authority Infraero, said authorities must wait for an analysis of the flight data and cockpit voice recorders to explain why the jet was going so fast.

"For some reason, the plane did not slow down," he said. "Something happened and the pilot, for some reason, accelerated the plane."

Brazilian aviation consultant Elias Gedeon said it was too early to assign blame: "The bottom line is we don't know what happened. Why was he going so fast? He couldn't stop? Was it the water on the runway? Was it his ability? We don't know."

Almost all airliners are equipped with thrust reversers that redirect the engines' jet blast forward to help slow them after touchdown.

While thrust reversers on twin-engine airliners such as the Airbus 320 are supposed to work in tandem, it's not unusual for only one to be deployed if the other is unserviceable.

The Congonhas airport recently resurfaced its runway to provide better braking in rainy conditions. But the new surface hadn't dried enough to cut deep grooves into the tarmac that allow water to run off the runway and provide increased grip. Airplanes continued to slide off the runway after the resurfacing was done and before Tuesday's crash.

Federal prosecutors are seeking an injunction to close Congonhas until the investigation is over, a process expected to take months. If a judge approves the move, it would cause air travel chaos throughout Brazil and severe financial repercussions for airlines.

In September, 154 people were killed when a Gol Airlines Boeing 737 collided with a small jet over the Amazon rainforest. Until Tuesday, that crash had been Brazil's deadliest.