Rescuers bring victims to the surface at the Soma mine, where 301 miners died.

Conflicting reports emerged as to what caused a mine fire and trapped miners underground. Some sources reported an explosion, while others pointed to a malfunction with the mine’s electrical distribution system, igniting a blaze. The mine’s shaft and ventilation system lost power. At the time of the incident, nearly 800 people were underground and authorities said most deaths have been carbon monoxide-related.

Owned by Soma Komur Isletmeleri AS, a subsidiary of the Soma Group, the asset lies about 300 miles southwest of Istanbul. In an email message quoted by Bloomberg, officials at the Soma Group said the incident took place despite the “highest safety measures and constant controls” and that an investigation is under way. Meanwhile, protestors furious over lax government regulations encircled Erdogan’s car, prompting him to shelter in a nearby store, according to Hurriyetnewspaper. Riot police also broke up rallies at company headquarters in Istanbul and Ankara.

Although mining accidents are frequent in Turkey, with more than 100 deaths reported since 2003, this incident is approaching the single “highest loss of life.”

Prior to the incident, Soma’s website called itself Turkey’s largest underground coal producer—producing 5.5 million tons per year—and that its Soma mine produces 250,000 tons a month (t/m), mostly supplied to a local power plant. Since then, however, the site has been taken down and replaced with a single message expressing condolences.

In a Q3 2012 interview with a Turkish newspaper, Alp Gurkan, the owner of Soma Holding, said his company had low operating costs, and outperformed estimates by state-run Turkiye Komur Isletmeleri, or TKI from which it purchased the asset in 1984. TKI had estimated Soma would cost $130-140 a ton to mine, while Gurkan’s company committed to $23.80 per ton, including a 15% royalty fee paid to TKI.

During the rescue operations, Labor Ministry officials, quoted by state-run news agency Anadolu, said the mine has been subject to five inspections since 2012 and, as of last month, no safety violations were reported. More recent reports say that inspectors rarely traveled underground and, when they did, they were shown the best parts of the mine.