Russia says it has cleared its Proton rockets for use after they were grounded last week following the loss of three satellites in a failed launch.

A government inquiry found the Dec. 5 failure was caused by over-fueling of a rocket's upper stage and not any design or technical issues, clearing the Proton class rocket to resume launches.

An investigated by a state commission of the failed launch, which resulted in the loss of three Russian Glonass navigation satellites, has cleared Proton's three lower stages from any involvement in the malfunction, Russian space officials said.

The Glonass launch used a new version of the Russian Block DM upper stage featuring larger propellant tanks.

Personnel fueling the upper stage for the launch did not account for the larger tanks and loaded between 2,200 pounds and 4,400 pounds more propellant than had been planned for the Glonass mission.

As a result of the excess propellant, the Proton's third stage, carrying excess weight, failed to place the satellites in orbit, and they crashed back into the Pacific Ocean.

Proton's next launch, set for the end of December, is a mission to lift a large commercial telecommunications satellite into orbit, officials said.