Twenty-nine New Zealand miners are missing after an explosion believed to have been caused by methane gas tore through the Pike River Coal Company mine on Friday afternoon. At the time of writing, there were no confirmed fatalities.

As of Saturday morning, 17 hours after the blast, concerns over air quality continued to prevent rescue workers from entering the Pike River Coal Company mine, which is located on the west coast of New Zealand’s South Island, in the Paparoa mountain ranges. Until Friday, it was the only producing coal mine in New Zealand.

It is feared the miners were killed in the blast, or that, if they survived, the breakdown of the mine’s ventilation system might have deprived them of oxygen. Officials said a rescue attempt might be initiated by the late afternoon on Saturday, 24 hours after the explosion in the mine.

The explosion was discovered by a mine electrician, Russell Smith. Smith went to investigate a power outage in the mine, presumably caused by the explosion, which may have taken place at 3:30 p.m. on Friday. There he found loader driver Daniel Rockhouse, 24, lying on the ground after having been knocked off his machine by the force of the blast.

Smith then manually pulled the mine alarm at 3:50 p.m., and he and Rockhouse were forced to climb up a narrow chimney— an air exchange with a ladder perhaps 300 feet high. From there they walked two more kilometres to alert authorities.

Pike River CEO Peter Whittall admitted that company officials learned something had gone wrong only at 4:10 p.m. No one has explained why it took so long for the company to become aware of the disaster, but it suggests that the mine’s emergency response system failed.

At the time of writing, nothing was known about the location of the 27 missing miners, although Whittall said they were probably between 2 and 2.5 kilometres into the mine at a depth of about 120 metres.

Pike River chairman John Dow said the mine has safe rooms, and miners are equipped with breathing kits powered by their own breath. However, emergency oxygen supplies in the mine are reportedly of limited volume. The mine has only two emergency exits, and it was not clear if these would be accessible to those trapped. One reporter who viewed the scene from a helicopter—before the National Party government of John Key imposed a no-fly zone—said that one of the emergency portals was badly burned. “I would say the outcome will not be good,” said the journalist, Paul McBride.

Family members of the missing miners gathered at the mine beginning on Friday night. Many are residents of Greymouth, population 10,000, located 46 kilometres to the southwest. Greymouth High School principal Jim Luders told the New Zealand Herald that 25 families with children in the school had connections to the missing miners.

“We are quite nervous, because a lot of our families are connected with the mine and we have former students who have headed off from the school to work in the mine,” Luders said. “They are real characters, great young students…. Everyone is quite connected because the mine is important here and it’s a tight community despite the fact they are from all over the world. They are South African, Australian and English as well as Greymouth families.”

A trade union official, Andrew Little, national secretary of the Engineering, Printing and Manufacturing Union, which collects dues from 71 of the 140 Pike River mine workers, rushed to defend the company.

“It’s only been in production for a year or so,” he said on Friday. “They delayed production because they weren’t satisfied that the ventilation system was right, so they’ve been pretty careful about that.”

The comment, meant to defend the mine’s management even before the dust had settled, may suggest that there were problems with the ventilation system. If air is not properly circulated out of a mine, methane gas can build up to the point that even a small spark will trigger an explosion.

Opened in 2009, the Pike River mine produces coking coal, which is used in the production of steel. It is 30 percent owned by New Zealand Oil and Gas, with smaller stakes held by India’s Gujarat NRE Coke and Saurashtra Fuels. The mine was due to produce as much as 360,000 metric tons of high-quality coal this year, most or all of it bound to feed Asia’a burgeoning steel factories. It is listed as one of New Zealand’s 50 largest corporations, with a market capitalisation of NZ$400 million.

However, the opening of the mine was beset by delays and cost overruns, taking startup overhead from an anticipated NZ$174 million to NZ$300 million and pushing back the commencement of production by 18 months. Among the delays was a rock collapse in the ventilation shaft and concerns over methane.

New Zealand Herald energy reporter Grant Bradley, who visited the mine while it was under development in 2008, said mine staff “referred to potentially explosive methane gas, which had been found in greater volumes than expected as tunnellers neared a fault deep below the Paparoa Ranges.” In order to reach two separate coal seams, the 2.3-kilometre mine shaft had to slope upwards into a mountain side, surpassing a fault line in the process, which another New Zealand publication described as “a 60m-wide zone of fractured rock with a risk of methane gas infiltration sufficient to require flameproof mining equipment to be used.”

Why methane gas should have built up to dangerous levels in the Pike River mine remains unclear, but it is possible that the cost overruns and delays may well have caused the firm to ramp up production at the expense of safety. It certainly would not be the first time such decisions have been made—to fatal consequences for workers.

The explosion at the Pike River mine is the latest in a series of major mine disasters that highlight the common dangers faced by workers in the extractive industries all over the world—dangers ultimately created by the insatiable drive for corporate profit. A very similar disaster took place in the US earlier this year, when on April 5, 29 coal miners at Massey Energy’s Upper Big Branch Mine were killed in a methane gas explosion caused by company indifference to ventilation and safety. In Chile, 33 gold miners were rescued last month after spending 69 days trapped far underground after a cave-in.

By far the worst situation confronts Chinese miners, who died last year at a rate of 7 per day in coal mine accidents. Last month, a mine explosion in Henan province killed 33.

The Pike River mine disaster is New Zealand’s first since 1967. Only about 6,000 workers are employed in mining in New Zealand, according to government statistics. The industry produced more than a billion New Zealand dollars (US$853 million) in export revenue last year.