A mysterious hole that appeared in the hull of a Soyuz space craft docked with the International Space Station in August was not caused by a micro-meteorite, according to one of the two cosmonauts tasked with investigating the breach during a December 12th space walk. Instead, it was drilled from inside the craft.

Sergei Prokopyev and fellow cosmonaut Oleg Kononenko returned to earth last week after completing their 197-day tour aboard the space station. Earlier this month, the two men executed a grueling 8-hour spacewalk in which they investigated and cut away portions of the spacecraft’s hull for further analysis back on earth. While the cosmonaut has made minimal statements regarding the hole directly to the media, he did state plainly that the hole originated on the spacecraft’s interior, adding that “it’s up to the investigative organs to judge when that hole was made.”

The hole was discovered in August when mission control noticed a slight drop on air pressure within the space station. The drop was considered minor, but the international crew quickly set about trying to find its source. Soon, a small hole was discovered in the hull of a Soyuz spacecraft launched from Russia that was docked with the space station. Initial debates revolved around how best to solve the problem, with mission commander and NASA astronaut Drew Feustel taking issue with the Russian plan to seal the hole without conducting any tests on the ground to make sure it would work. Ultimately, Roscosmos disregarded Feustel’s concerns and ordered their cosmonauts to make the repair.

After the immediate danger had passed, questions about how the hole appeared became the most pressing. It wasn’t long before images surfaced that appeared to show tool marks around the hole, and soon thereafter, Russian officials issued a statement indicating that sabotage was a possible cause.

“It is a matter of honor for Energia Rocket and Space Corporation to find the one responsible for that, to find out whether it was an accidental defect or a deliberate spoilage and where it was done — either on Earth or in space. Now it is essential to see the reason, to learn the name of the one responsible for that. And we will find out, without fail,” Dmitry Rogozin, CEO of Roscosmos, told Russian state media.

Two cosmonauts and an American astronaut then had to make the trek back home in that very capsule, though there was no danger posed by the hole: it was drilled through a portion that is jettisoned prior to the vehicle’s reentry.