At least 12 people were killed and several others injured in a blast in a Murmansk region mine where raw materials are extracted for producing fertilizers, officials said Friday.

The blast at the Rasvumchorrsky mine, outside the Arctic town of Kirovsk, occurred at around 8:30 p.m. Thursday as workers were arranging explosives in preparation for a controlled blast, Irina Gretskaya, a regional Emergency Situations Ministry spokeswoman said by telephone.

"A fire broke out after the blast, and 18 people were at the site," Gretskaya said. "Six managed to escape from the mine and were hospitalized with various injuries. The rescue teams later found the bodies of 12 other workers."

The mine is owned by Apatit, a major producer of apatite, a phosphate mineral used in most fertilizers. The company is owned by PhosAgro, a domestic producer of complex fertilizers.

At the time of the explosion, workers had already placed 18 tons of explosives and were planning to place another 30 tons ahead of the controlled blast, which was scheduled for Monday, Apatit spokeswoman Vera Belousova said.

Regional prosecutors opened a criminal investigation in connection with possible safety violations leading to the explosion, said Galina Mashyanova, a spokeswoman for the Murmansk Regional Prosecutor's Office. The region's top prosecutor, Maxim Yershov, has taken personal control of the investigation, Mashyanova said.

The country's industrial safety watchdog said it had created a special commission to determine the cause of the blast.

"Our purpose is not to revoke the companies' licenses, but rather to prevent such accidents and to improve the safety conditions both at this site and similar ones," said Alexei Shpagin, a spokesman for the Federal Service for Ecological, Technological and Atomic Inspection.

Apatit said in a statement Friday that it had suspended operations at the Rasvumchorrsky mine indefinitely. The company operates three other mines in the region, containing an estimated 3.5 billion tons of phosphate ore.