“Something stinks in here” (literally)… Astronauts on the International Space Station (ISS) encountered a strange and unwelcome arrival when a Russian spacecraft docked: a foul smell, Newsweek reports.

The “unexpected smell” was detected when the Progress 90 cargo spacecraft — carrying several tons of food, fuel and supplies — docked with the Russian Poisk module of the ISS on Saturday, disturbing the Russian cosmonauts who opened the hatch with its odor.

Along with the noxious smell, the cosmonauts also noticed droplets floating in the air, prompting the hatch to Progress to be immediately closed, and the Russian craft isolated from the rest of the ISS while air quality levels were checked.

Anatoly Jacques, who writes for the independent space-tracking website Russian Space Web, said the smell was “toxic” and that NASA astronaut Don Pettit said it resembled “spray paint”.

The Houston base eventually determined that there were no hazardous gases on the ISS, and as of Sunday afternoon, astronauts began the process to reopen the hatches on Progress, while all other space station operations are proceeding as planned.

The origin of the smell remains unknown, but Russian spacecraft have experienced leaks in the past. Newsweek reached out to Roscosmos for comment, but did not immediately receive a response.

The International Space Station is arguably the most expensive man-made structure ever built, costing around €120 billion. It is not owned by any country or company, but is a collective effort, and operates through international partnerships. NASA provides the majority of funding. The European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA) and the Canadian Space Agency (CSA) are also involved in science experiments on the station.

The ISS continues to serve as a hub for international cooperation, with Moscow saying it will support the station until 2028, with international operations expected to continue until 2030.