The failed Russian Phobos-Grunt Mars probe is falling from orbit and may hit Earth as soon as Sunday.

The 13.2-ton probe was launched in November on a mission to explore the Martian moon Phobos. But the craft became stuck in orbit when its computer malfunctioned and rocket boosters failed.

Russian space experts are unsure of where pieces of the probe will land, but expect between 20 and 30 pieces to impact the Earth.

The space debris could include some radioactive material, but the Russian space agency does not expect the material will cause a health risk.

The failed Phobus-Grunt project is among several major setbacks the Russian space agency has suffered. The head of Russia's space program, in an interview published Tuesday, hinted that foreign forces may be behind the recent failures of Russian spacecraft.

Roscosmos chief Vladimir Popovkin told the daily newspaper Izvestia that modern technology makes spacecraft vulnerable to foreign influence. But he said it is unclear why some Russian craft have malfunctioned while flying beyond the reach of the nation's tracking equipment.

In addition to Russia losing the Phobos-Grunt Mars probe, an unmanned launch attempt in August experienced a catastrophic failure.

Russia is the only nation transporting crew members to and from the International Space Station since the United States retired its space shuttle program in July.