Krikalyov did not explain what caused the sensor to malfunction but said the agency was working to prevent the issue on future flights.
Presenting findings of an official inquiry into the accident, chief investigator Igor Skorobogatov said two more Soyuz rockets might have the same defect and that new checks were now being introduced into the rocket assembly process.
The Russian rocket that carried two people to space last month failed and sent the craft back to Earth because of "deformation" of a part that was made during assembly at the cosmodrome, a space official said on November 1.
The camera mounted on the rocket showed the moment of a failed separation of the first and second stages.
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They were students who were accompanying their brother in Washington, according to the Royal Consulate General of Saudia Arabia. The sisters, originally from Saudi Arabia , were found clothed in fur trim coats and bound together with duct tape.
The accident was the first involving a manned launch since the Soviet era and delivered another blow to the image of Russia's space programme after embarrassing losses of satellites and of an unmanned cargo ship in 2015. They had been due to land on December 13.
"We have to draw conclusions from every emergency situation", said Roscosmos deputy director Alexander Lopatin, adding that Russian Federation has discussed the findings of the probe with Nasa.
Following the investigation by the space experts, "appropriate law enforcement authorities" will work out who is guilty of the assembly mistake, said Roscosmos deputy head Alexander Lopatin.
Russian space officials say they hope to resume sending crews to the International Space Station on December 3 after an October launch failed because of a technical malfunction.
Krikalev said the next launch will now be moved forward to December 3, and will carry the same crew as originally intended on this mission, MS-11: Russian Oleg Kononenko, American Anne McClain, and Canadian David Saint-Jacques.
"The reason found by the commission (investigating the accident) was the abnormal operation of a sensor that signals the separation of the first and second stages", Krikalyov said at a space industry event in Moscow.