Conflicting reports are emerging as to what caused flames and methane gas to trap some 150 Turkish coal miners underground as the death toll in one of the nation’s worst mining disasters has risen to 274. Some sources have reported an explosion and others pointed to a malfunction with the mine’s electrical distribution system, igniting a blaze 420 m deep. An electrical trade union is disputing this assertion. At the time of the incident nearly 800 people were underground and authorities said most deaths have been carbon monoxide-related.

Since the fire erupted at the Soma mine project at 3 p.m. Tuesday, according to authorities, more than 360 miners have been rescued, while between 125 and 150 others remain unaccounted for. Owned by Soma Komur Isletmeleri AS, a subsidiary of the Soma Group, the asset lies about 300 miles southwest of Istanbul.

Given the fire intensity, “our hopes are fading,” Energy Minister Taner Yildiz, who is overseeing 400 rescuers, said Wednesday. The incident occurred during a shift change, leaving 787 miners inside, increasing casualties, said officials; shaft elevators were also reportedly useless. Other miners on other levels, however, were trickling out on their own.

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. On Wednesday, meanwhile, protestors furious over lax government regulations encircled Erdogan’s car, prompting him to shelter in a nearby store, according to Hurriyet newspaper. 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,” Yildiz told NTV television; Turkey’s worst mining accident occurred in 1992 when 263 died in a methane explosion at a project near the northwest Black Sea port of Zonguldak, which Soma has run since 2011.
Rescuers reportedly ceased operations Wednesday night and restored ventilation to evacuate smoke and CO.

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.

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. However, “if there is negligence, we won’t remain indifferent,” Energy Minister Yildiz said.

Lawmakers from Turkey’s lead opposition group, the Republican People’s Party, however, said President Erdogan’s ruling party voted down a proposal on April 29 for a formal inquiry into a series of small-scale accidents at mines around Soma.