"The launch of another Proton booster rocket, scheduled for June 20, is likely to be postponed," head of the Commission, Deputy Director General of the TsNIImash company Alexander Danilyuk said.
"June 8 is the probe deadline," he said, noting that the priority version focused on damage to a turbine pump bearing.
"The findings are not going to be sensational," he added.
After the commission finishes its work, a decision will be made on resuming the use of Protons. "My opinion is that they won't fly this month," Danilyuk said.
A Baikonur spaceport source told ITAR-TASS on Tuesday that the launch of the Proton-M booster with a Russian satellite, scheduled for June 20, had been postponed to July 8.
In the May 16 accident, the rocket, intended to take a communications satellite into orbit, began its flight from Baikonur at 01.42 Moscow time, burning up in dense layers of the atmosphere above the Pacific.
Early reports said the engine malfunctioned, presumably because of a faulty guidance system of the third stage, in the 545th second of the flight when Proton was at a height of 161 kilometres.
In the previous accident involving the Proton booster on July 2, 2013, Russia lost three Glonass-M satellite navigation units. The accident occurred due to faulty installation of angular rate sensors during booster rocket assembly in November 2011.