A small hole found in the hull of a Russian Soyuz capsule docked with the International Space Station has been found to have been deliberately drilled, puzzling officials as to why anyone would damage a manned spacecraft in such a dangerous manner.

The 2-milimeter (0.08-inch) hole was discovered by the ISS’s crew on August 30, when it was found that the station was experiencing a pressure drop from the night before, indicating a small leak in the hull. The station’s astronauts and cosmonauts tracked the leak to the Soyuz MS-09 spacecraft, currently docked to the Russian Rassvet module. This capsule had ferried three of Expedition 56’s crew members into orbit last June: cosmonaut Sergey Prokopyev, European Space Agency astronaut Alexander Gerst and NASA flight engineer Serena Auñón-Chancellor.

Initially thought to be a hole punched through the hull by a micrometeorite, Russian engineers quickly realized that the hole was not only made from inside the capsule–ruling out an impact from the outside–but that the area around the hole also bore marks where a drill head had scraped the paint off of the damaged component.

But was this a mistake on the part of whomever drilled the hole, or was it an attempt at deliberate sabotage? "We are considering all the theories," explained Dmitry Rogozin, director general of Russian’s space agency, Roscosmos, in a statement made to TASS. "The one about a meteorite impact has been rejected because the spaceship’s hull was evidently impacted from inside.

"It was done by a human hand, there are traces of a drill sliding along the surface. We don’t reject any theories."

Prokopyev and fellow cosmonaut Oleg Artemyev plugged the hole with a layer of gauze tape soaked in epoxy, allowing flight control to restore normal pressure to the cabin. Thankfully, due to the hole’s small size, the crew wasn’t in any danger, and the portion of the Soyuz capsule that the hole was in is sealed off and jettisoned before reentry.

RSC Energia, the Russian company that manufactures the Soyuz spacecraft, is currently carrying out detailed inspections of all Soyuz spacecraft being prepared for launch, as well as their fleet of Progress supply ships, looking for signs of similar damage. But the investigators still haven’t determined if the hole was drilled on the ground prior to launch, or if it had been made by one of Expedition 56’s crew while in orbit.

According to Rogozin, "it is a matter of honor for Energy Rocket and Space Corporation (RSC Energia) 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."

Russian news agency RIA Novosti reports that a source from RSC Energia told them that the culprit had been identified as a ground technician that had mistakenly drilled through the hull, and patched up the mistake with a sealant. The makeshift seal apparently failed on August 29, allowing the drilled hole to leak air from the ISS.