The U.S. space agency says astronauts on the space shuttle Discovery may need to repair the craft before it heads back to earth.
Discovery's flight director, Paul Hill, said Sunday that NASA engineers have seen small bumps on the shuttle's filler material--which seals the space between thermal tiles.
He says engineers are trying to determine whether the filler must be fixed before Discovery returns to Earth.
News of the problem came as the shuttle's astronauts unloaded 15 tons of supplies at the International Space Station. NASA officials concede that further work at the space station may have to go ahead without the help of U.S. orbiters.
Last week, NASA again grounded its fleet after a piece of foam broke off from Discovery's external fuel tank during launch.
Loose foam was blamed for the 2003 Columbia disaster, which killed the seven astronauts aboard as they re-entered earth's atmosphere.
Information for this report is provided by AP, AFP and Reuters.