Alarm reported on space station, crew safe

HOUSTON, TX -- An early morning alarm on the International Space Station forced US astronauts to evacuate to the Russian side of the space station.

The alarm went off around 3 a.m. CT in the US segment of the complex. That alarm is sometimes indicative of an emergency ammonia leak.

The crew immediately put on masks, moved into the Russian segment of the space station and closed off the US segment. The crew checked the air readings which were all within limits. The crew was then allowed to remove their masks.

NASA mission control in Houston immediately began investigating. During a media briefing at 7:55 a.m., NASA reported that there is no hard data to suggest that there was in fact an ammonia leak. At this time, NASA thinks issue was a card failure inside one of computers that takes various measurements and transmits systems data to Houston.

"Big picture perspective: We're still trying to figure out exactly what happened. We're still not entirely convinced this was an ammonia leak," Mission Control told the ISS crew.

NASA says there was an increase in pressure in one of the water loops, which may have triggered the alarm. Non-essential equipment was powered down in the US segment, but mission control is now working to turn those systems back on.

NASA is hoping to get US astronauts back into their section by tonight.

Keep checking back on this page to get real-time updates as this story unfolds.