NASA is reportedly investigating a claim that an astronaut accessed the bank account of her estranged spouse from the International Space Station (ISS) — in what could be the first allegation of a crime committed in space.

American astronaut Anne McClain, who has since returned to earth, acknowledged she had accessed the account from the ISS but denied any wrongdoing, according to the New York Times.

Speaking through her lawyer, Lieutenant Colonel McClain told the New York Times she was only making sure that the family’s finances were in order and that there was enough money to pay bills and care for her partner’s son.

“She strenuously denies that she did anything improper,” her lawyer said adding that the astronaut was “totally cooperating”.

But the astronaut’s partner, Summer Worden — a former Air Force intelligence officer living in Kansas — felt differently, filing a complaint with the Federal Trade Commission (FTC) and another with NASA’s Office of Inspector General, accusing Lieutenant Colonel McClain of identity theft.

“I was pretty appalled that she would go that far. I knew it was not OK,” Ms Worden said, who added the FTC had not responded to the identity theft report.

NASA officials told the New York Times they were not aware of any crimes committed on the space station.

There are five international space agencies involved in the ISS — the US, Canada, Japan, Russia and the European Space Agency — and their agreed legal frameworks stipulate that national law applies to any people and possessions in space, meaning Americans are subject to American law in space, and Russians subject to Russian law, etc.

Lieutenant Colonel McClain was on board the recent launch of Soyuz MS-11 to the ISS in December 2018 as a flight engineer. She performed her first spacewalk on March 22, 2019, in a six-hour-and-39-minute EVA.

She was scheduled to perform a second EVA on March 29 alongside Christina Koch, which would have been the first all-female spacewalk, but spacesuit sizing issues saw Lieutenant Colonel McClain reassigned.

A NASA spokeswoman told the New York Times the decision over the spacewalk was not influenced by any allegations about Lieutenant Colonel McClain.

Lieutenant Colonel McClain returned to Earth on June 24.