Three workers were killed in an underground collapse at one of Western Europe’s largest potash mines in northeastern Spain, according to the regional union USOC.

The mine collapse occurred just before 9 a.m. local time (0800 GMT) about 900 meters underground, firefighters said, without providing further details.

Two of the dead were students at the Polytechnical University of Catalonia, the university said on Twitter.

“We want to send our deepest condolences to the families of the three colleagues who lost their lives this morning doing their work,” USOC said.

Tel Aviv-based ICL Group Ltd, whose subsidiary Iberpotash operates the mine, said there had been an “unfortunate underground accident”, in a statement released before the deaths were announced.

Authorities are unable for now to confirm the deaths but fear the worst, Joan Ignasi Elena, head of the interior department at the Catalan regional government, told a news conference. He said they could not identify the miners until they were reached, which could take several hours. The remaining workers at the mine were evacuated, he added.

The mine is about 80 km (50 miles) north of Barcelona. Catalonia’s business department top official Roger Torrent said it had passed a safety inspection in February.

In December 2013, Iberpotash said two of its workers died after a mine collapse in Suria. Local media reported that a 46-year-old worker died in June 2020 at the company’s Vilafruns mine in Balsareny in Barcelona province when a rock fell on him. Three weeks later, a 55-year-old miner died under similar circumstances in a separate accident. The Vilafruns mine was shut down that year.

Potash is used as a fertilizer in agriculture and as a raw material in industries such as pharmaceutical, explosives, glassmaking and chemicals.

Potash prices have soared in the past year after the European Union sanctioned major supplier Belarus over its support for Russia’s invasion of Ukraine production.