The space habitat development company Bigelow Aerospace tweeted on Tuesday that two inoperative satellites, the US’s Genesis II and Russia’s Soviet-era Cosmos 1300, might collide.

While the odds of a crash are only 5.6 percent, Bigelow Aerospace, the owner of Genesis II, says it’s another troubling sign that Earth’s orbit is becoming dangerously crowded.

Bigelow Aerospace followed up with a warning about the rapid proliferation of space junk, a problem raised earlier when one of SpaceX’s numerous StarLink satellites nearly crashed into a European Space Agency observation satellite.

“This proliferation, if not controlled in number, could become very dangerous to human life in low Earth orbit,” Bigelow Aerospace tweeted.

The Bigelow Aerospace Genesis-2 module, designed to test the technology of commercial space stations, was launched into orbit in June 2007 and worked for about 2.5 years. The developer planned to create a commercial space station from transformable modules.

The Soviet-era satellite Cosmos-1300 was launched in August 1981 as part of the Tselina-D military space-based radio surveillance system.