Unexpected space debris came flying close to the International Space Station on Tuesday, prompting its six astronauts to take shelter inside two Soyuz capsules, NASA said.

The "trash" came within about 250 meters (820 feet) of the station, CNN reported. Three minutes later, at 8:11 a.m. ET, the all-clear was sounded and astronauts were allowed to exit the capsules. An investigation by NASA is underway.