The US space agency has said it is too early to say whether the crew faces any danger. But after Columbia's disintegration on February 1, 2003 was blamed on a piece of insulation foam that fell off, NASA is extremely sensitive to any alert with the shuttle.

"The engineering community doesn't think that this is going to be a significant issue," an upbeat lead shuttle flight director Paul Hill reassured reporters at a briefing.

"I expected that we would shed some small tolerable amount of debris," he said, underscoring that in his view "everything is going extremely well."

Twenty-four hours after the blast-off, the first by a shuttle since the Columbia disaster in 2003, the crew used special cameras to study the wings and nose of Discovery.

NASA experts on the ground scanned photographs from the launch for signs that a piece of tile and a larger object seen flying off the shuttle on Tuesday could have caused damage that needs repair.

An examination of the edges of the wings and the nose of the shuttle was conducted by a special laser scanner and infrared camera at the end of a 15-meter (50-foot) extension to the shuttle's robotic arm.

The operation focused on thermal tiles on the rounded edges of the wings and the tip of the shuttle.

NASA wants to clear up any doubts before the shuttle docks with the International Space Station (ISS) on Thursday.

Discovery lifted off from the Kennedy Space Center in Florida on Tuesday amid cheers and some tears from ground experts who had been working for two and a half years to get the shuttle back into space.

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