Russia’s space agency said on Wednesday that an investigation has found that a rocket carrying a crew to the International Space Station failed three weeks ago because of a technical malfunction of a sensor.

The Soyuz-FG rocket carrying a NASA astronaut and a Roscosmos cosmonaut failed two minutes into the Oct. 11 flight, sending their emergency capsule into a sharp fall back to Earth. They landed safely on a steppe in Kazakhstan, but the aborted mission dealt another blow to the troubled Russian space program that serves as the only way to deliver astronauts to the orbiting outpost.

Roscosmos’ executive director Sergei Krikalyov said Wednesday the probe found that a malfunction of a sensor which signals the jettisoning one of the rocket’s four side boosters caused the booster to collide with the second stage of the rocket.

Krikalyov stopped short of saying why the sensor had malfunctioned but said the space agency is working to ensure such incidents do not happen again.

Russian space officials plan to conduct one more unmanned Soyuz launch from Russia and one abroad before launching a crew to the space station.

Krikalyov said they hope to send the new crew to the orbiting lab on Dec. 3. That would also mean that the current crew will have to stay there for at least an extra week or two to ensure a smooth carry-over.

(AP)