Astronauts on the linked shuttle Atlantis and International Space Station said Friday that they're not worried about recent false alarms that disrupted their sleep with erroneous reports of calamity.

"I think they're still trying to get the full comprehensive story together," Atlantis commander Charlie Hobaugh said Friday. "I think they've got a pretty good idea of what happened, but it wasn't really that big of a deal."

Shortly after 8:30 p.m. EST Thursday (0130 Friday GMT), the 12 astronauts onboard the orbiting laboratory were startled by an alarm warning them that the station was losing pressure. They flew into action to investigate the problem, but by 9:15 p.m. EST Mission Control teams on the ground had determined there was no depressurization going on.

"The crew was never in any danger," NASA said in a statement.

The main alarm shut off ventilation fans, which kicked up dust that set off a fire alarm in another part of the station.

If real, a depressurization would be no minor trial. It would mean that air from the cabin was leaking out into the vacuum of space. NASA is still looking into the cause of the false alarm.

Hobaugh said the shuttle and station crews had only recently ended their day and gone to bed, so some astronauts didn't even lose much sleep over the issue.

"It was kind of fun to get everybody together and say, 'Hey, what's going on?" and we went back to sleep, so not a big deal," Hobaugh said.

The erroneous warning did not interrupt any major plans for the seven-person shuttle crew or the five-person station crew. Atlantis is scheduled to return home to Earth Nov. 27, ending an 11-day supply mission to the orbiting outpost and ferrying long-term station crewmember Nicole Stott, a NASA astronaut, back home along with the shuttle crew.

The shuttle astronauts are preparing for the second of three spacewalks planned for their mission, set to begin at 8:18 a.m. EST (1318 GMT) Saturday.