MOSCOW (AP) — Russia will postpone the launch of an empty space capsule to the International Space Station pending further investigation of a coolant leak on a supply ship docked to the station, the second such leak at a docked Russian craft in two months, the head of Russia's space corporation Roscosmos said Monday.

The Soyuz capsule was to be launched in automatic mode on Feb. 20 and dock with the orbiting outpost two days later, to serve as a lifeboat for crew evacuation in case of an emergency. Roscosmos director Yuri Borisov said the launch will delayed, at most until early March.

A Soyuz capsule that can accommodate an astronaut capsule and was already docked to the station developed a coolant leak in December.

Russians Sergey Prokopyev and Dmitri Petelin and NASA astronaut Frank Rubio were supposed to return to Earth in March in that capsule, but Russian space officials said higher temperatures from the coolant leak could make that dangerous.

Then another coolant leak was detected Saturday in a docked supply ship. The leak was detected after a second supply ship docked with the space station.

Borisov said the unmanned Soyuz launch would be delayed “until we make sure and get to the site of a possible breakdown.”

Because the new Soyuz will be launched in automatic mode, a replacement crew will now have to wait until late summer or fall when another capsule is ready. That means Prokopyev, Petelin and Rubio will have to stay several extra months at the station, possibly pushing their mission to close to a year.

Besides Prokopyev, Petelin and Rubio, the space station is home to NASA astronauts Nicole Mann and Josh Cassada; Russian Anna Kikina; and Japan’s Koichi Wakata. The four rode up on a SpaceX capsule last October.