A Russian weapons test created more than 1,500 pieces of space junk that is now threatening the seven astronauts aboard the International Space Station, U.S. officials said Monday.

The State Department confirmed that the debris was from an old Russian satellite destroyed in Monday's anti-satellite weapons test.

"It was dangerous. It was reckless. It was irresponsible," said State Department spokesman Ned Price.

Earlier Monday, the four Americans, one German and two Russians on board were forced to seek shelter in their docked capsules because of the debris.

At least 1,500 pieces of the destroyed satellite were sizable enough to show up on radar, Price said.

After decades of uncertainty, researchers have confirmed the existence of lunar carbon dioxide cold traps that could potentially contain solid carbon dioxide. The discovery will likely have a major influence in shaping future lunar missions and could impact the feasibility of a sustained robot or human presence on the moon.

The United States said Monday it was investigating a "debris-generating event in outer space" after astronauts on the International Space Station were forced to prepare for a possible evacuation.

The incident came amid unconfirmed reports that Russia had carried out an anti-satellite weapon (ASAT) test—rare show-of-force demonstrations criticized by the space community because of the risk they create for crews in low Earth orbit.

"US Space Command is aware of a debris-generating event in outer space. We are actively working to characterize the debris field and will continue to ensure all space-faring nations have the information necessary to maneuver satellites if impacted," the military branch said.

"We are also in the process of working with... the State Department and NASA, concerning these reports and will provide an update in the near future.