MOSCOW, February 12. /TASS/. The source of leak from the thermal system of the Progress MS-21 spacecraft has not yet been examined, and Russian experts will ponder on possible ways of doing so, Roscosmos executive director for manned space programs Sergey Krikalev said on Saturday.

"Regretfully, the exact spot [where the leak occurred] is not visible. We need to think on ways to see how the hole looks like and what could have been the cause, because an external survey with detailed high-quality images will help to narrow down the search for answers," Krikalev said.

A drop in pressure was detected aboard the Progress MS-21 freighter, which was expected to end its mission at the International Space Station (ISS) on February 18. The spacecraft has been isolated from the ISS. Roscosmos said the causes of depressurization were being investigated, and emphasized that it had no effect on either the docking of the Progress MS-22 cargo spacecraft to the ISS or the schedule of space activities aboard the ISS.