A piece of debris falls off the external fuel tank during the launch.
KENNEDY SPACE CENTER, Florida (CNN) -- There will be no more shuttle launches until NASA engineers determine the effect of debris that fell from the shuttle Discovery during blastoff Tuesday, said Bill Parsons, space shuttle program manager.
"We are treating it very seriously," he told reporters. "Are we losing sleep over it? Not yet."
He added, "We will continue to do the evaluation."
Discovery is due to return to Kennedy Space Center in Florida on August 7.
The date of the next planned mission had not been set.
Earlier Wednesday NASA lead flight director Paul Hill said that, based on engineers' "first-blush" analysis of falling debris, there was "no significant problem" with the orbiting shuttle.
Hill spoke to reporters after astronauts, using a robotic arm equipped with a camera and laser, spent "one hell of a day" poring over every inch of Discovery, looking for surface damage.
Although the mission had been scheduled to search for damage, concern about the issue was heightened after videotape from an array of cameras trained on Discovery during Tuesday's liftoff showed a piece of debris falling away from the underside of the orbiter.
NASA officials said the debris could have broken off from a tile near a door covering the nose landing gear. Space shuttles have shed tile during previous missions without consequences.
But falling debris from the shuttle Columbia during its ascent was blamed for damage to the craft that led to its destruction and the deaths of all seven crew members upon its re-entry into Earth's atmosphere in February 2003.
The subsequent grounding of the shuttle fleet and the investigation into the disaster prompted NASA to make safety-related activities a priority for this first post-Columbia mission.
Appearing at a news conference at Johnson Space Center in Houston, Texas, Hill said that NASA engineers' "first blush, when they looked at this, was it wasn't going to be a significant problem." But, he added, engineers have seen "some things" in video from the launch that cause "some concern."
"This has been one hell of a day," Hill said, referring to Discovery's seven-member crew's operation of the 50-foot robotic arm and its 50-foot boom extension. "The crew has had three crew members fully employed, doing nothing but this all day long. And when any of the rest of them had a spare moment, they were also there helping to look out the windows and look at camera views."
NASA was analyzing data from video and from the robotic arm, the launch and elsewhere to decide what steps -- if any -- to take next.
"We should start seeing the jury coming in on those decisions by the end of the crew's day tomorrow," Hill said. "My guess is we're not going to have a problem."
At a Tuesday news conference, NASA flight operations manager John Shannon predicted that the space agency would have enough information by Sunday to decide whether any repairs are needed and, if so, whether such repairs would be possible.
Shannon said the initial estimate of the debris showed it was about 1.5 inches long. He said it might be the tile covering rather than the tile itself.
Footage of Discovery's launch also showed a piece of debris falling from the external fuel tank at the time it separated from the orbiter, Shannon said. However, it did not strike the orbiter, he said.
Footage also showed that the external fuel tank's nose cone hit a bird about 2.5 seconds after liftoff -- when Discovery was probably traveling too slowly to sustain any damage, he said.
Hill said it has not been lost on controllers that this is the first mission after the Columbia disaster.
"We have seven folks living on this space shuttle and counting on us to do the right thing and keep them safe and not to get all giddy and high-fiving each other," he said.
"There's a certain amount of almost shock that we really are here, we really are doing these things that so many folks ... thought that we couldn't do."
As the orbiter approaches the international space station for a scheduled Thursday 7:18 a.m. ET docking, the station's crew will photograph Discovery to look further for any damage.
Shuttle crew members plan to test repair techniques during three scheduled space walks by astronauts Steve Robinson and Soichi Noguchi of Japan. During their space walks, Robinson and Noguchi also plan to service the space station.
As part of the safety changes instituted after Columbia, NASA developed contingency plans for astronauts to try to repair damaged shuttles so they can return to Earth. In the event a spacecraft cannot be repaired, plans call for the crew to take refuge in the space station until a rescue mission can be launched.
CNN's Miles O'Brien, Marsha Walton and Kate Tobin contributed to this report.