NASA Administrator Jim Bridenstine vowed Thursday to speak to the head of the Russian space agency after reports that the cause of a hole found on the International Space Station last year would be kept secret.

But he was careful to point out that he doesn't want this situation to destroy the country's relationship with Russia, a partner in space since 1975.

"They have not told me anything," Bridenstine told the Houston Chronicle during a question and answer session at a Houston energy conference. "I don't want to let one item set (the relationship) back, but it is clearly not acceptable that there are holes in the International Space Station."

A hole that was allowing air to escape was discovered Aug. 30 in a Russian Soyuz spacecraft attached to the station. The crew was able to plug the hole quickly without any adverse effects on board. But if left unchecked, the leak could have resulted in total air loss for the station in 18 days.

Initial reports indicated that it was the result of space debris, but it was later determined that it likely was the result of sloppy drill work, either here or in space. A Russian suggestion of American sabotage did not sit well with NASA personnel and astronauts.

Dmitry Rogozin, head of the Russian space agency Roscosmos, said Wednesday the country had finally determined what caused the hole. But Russia wasn't going to tell anyone, he said.

"What happened is clear to us, but we won't tell you anything," Rogozin said, according to the state-run news agency RIA Novosti.

The hole -- and its now secret cause -- is especially problematic because the Soyuz has been the only way to ferry astronauts to and from the station since 2011, when the space shuttle program was shuttered. NASA pays Russia $82 million per seat for a ride on the Soyuz.

Bridenstine told the Chronicle that the hole could have been caused by a defect before it launched, or potentially a result of something after it was on orbit. Only Russia knows for sure.

The incident highlights the need for SpaceX and Boeing to launch their commercial crew vehicles, which they have been working on since 2014 to take astronauts to and from the space station.

But both companies failed to meet their launch deadlines in 2018 and have continued to struggle. It's not clear when they will do their first test flights with astronauts on board.

Alex Stuckey writes about NASA and science for the Houston Chronicle. You can reach her at alex.stuckey@chron.com or Twitter.com/alexdstuckey.

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NASA leader vows to seek answers about space station from Russia - Houston Chronicle