Rescuers were struggling on Thursday to reach three people trapped deep underground after an accident at a Spanish potash mine, with officials admitting they "feared the worst".

"The information we have makes us fear the worst," regional interior minister Joan Ignasi Elena told reporters outside Cabanasses mine in Suria, 75 kilometres (46 miles) northwest of Barcelona.

Rescuers said they were trapped "at a depth of about 900 metres" (2,950 feet) after one of the galleries collapsed just before 9:00 am (0800 GMT).

With experts still trying to reach them, the minister said he was unable to officially confirm they had died.

"The authorities that could confirm this haven't been able to reach them yet because we have to ensure their safety," he said, indicating it would be "reckless" to rush such an operation.

Efforts to reach the trio were likely to continue "for the next few hours", tweeted the Catalan regional fire service.

Earlier, Catalan regional leader Pere Aragones said on Twitter that the three had died: "We deeply regret the death of the three miners in the accident in Suria mine."

But he deleted the tweet several minutes later.

Many local and national media outlets had also said the three had died, quoting sources among the rescue services.

But police said they could only confirm whether they were dead or alive "when they were reached by a doctor" and their families had been notified.

They dispatched several specialist units to the site while the emergency services sent in two medical helicopters and a team of psychologists.

- 'No warning' -
 

When the gallery collapsed, all three were carrying out "a routine task that they do every day", mine worker Carlos Arnaldo told reporters at the scene.

He said it was "difficult" for him to believe that they might have survived.

"Sometimes the mine gives you no warning: the roof caves in and nothing can be done," he said.

"This is terrible news," tweeted Labour Minister Yolanda Diaz, sending "love and solidarity to the families and colleagues of the workers caught up in the collapse at the Suria mine".

Owned by ICL Iberia, the Spanish arm of Israel's ICL Group, which specialises in fertilisers and chemicals, the Cabanasses mine had recently passed a security inspection, officials said.

"The last inspection was just three weeks ago and it was cleared without any sign of irregularities," Catalan regional business minister Roger Torrent told reporters at the scene.

ICL Iberia is the only company that produces potassium salts in Spain, handling both the extraction, treatment and marketing, its website says.

Based in Suria, it has 1,100 employees.

Two miners died in December 2013 when a gallery collapsed at the same mine, the Catalan press reported at the time, citing an official statement.

The last major mining accident in Spain was two months earlier, in October 2013, when six people were killed and five others injured following a gas leak at a coal mine in the northwest.

It was the worst accident at a Spanish mine since 14 miners were killed in August 1995 during a methane explosion at a coal mine in the northern province of Asturias.