NASA is examining seven heat shield tiles that appear to have been damaged during the shuttle Endeavour's ascent into orbit, but the US space agency said Wednesday there was no cause for concern.
"We don't have any reason for concern or alarm," said Leroy Cain, deputy shuttle program manager.
"We are very much in the middle of this process. I wanted to show you some areas we are working on," he told reporters.
Graphics depicting seven chipped tiles on the underside of the orbiter were broadcast during a routine press conference at the end of Day 3 of the shuttle mission, with three tiles highlighted in yellow as of particular interest to NASA, Cain said.
Astronauts were able to capture high resolution photos of the shuttle's exterior when it approached the International Space Station earlier Wednesday, doing a nine-minute, 360-degree flip before docking at the orbiting lab.
The crew is equipped with kits to repair damaged tiles if needed. Shuttle managers would know more about what steps, if any, should be taken in the coming days, Cain said.
The shuttle Columbia disintegrated in 2003 during its fiery re-entry toward Earth after its heat shield was damaged by a piece of foam that broke off the external fuel tank during launch, weakening the shuttle's protective cover.
NASA has taken care to closely examine the shuttle's heat shield after liftoff ever since.
Endeavour is the second to last mission of the US shuttle program, which will end later this year after the final launch by Atlantis.
Explore further: NASA still plans May shuttle launch