WELLINGTON, New Zealand – Poisonous gases kept rescuers from entering a New Zealand coal mine where a powerful blast trapped 29 workers, as intermittent power outages Saturday frustrated efforts to pump in fresh air.

Two men emerged after the explosion Friday, but there has been no word from the 29 others. Anguished relatives voiced frustration over the delays in the rescue operation.

"If I had my way I'd be down there, I'd go into the mine myself," said Laurie Drew, whose 21-year-old son, Zen, is one of the missing men.

Rescue organizers said the level of methane and carbon monoxide was still too high Saturday to send a crew into the Pike River Mine. Police said the miners, aged 17 to 62, are believed to be about 1.2 miles (two kilometers) down the main tunnel.

"Unfortunately it's just not as simple as putting on a mask and gown and rushing in there," the police search controller, superintendent Gary Knowles, told TV One. "It does pose a danger to those guys underground and ... a danger to the staff going in."

Knowles said the rescuers would remain on standby until the gases were next checked early Sunday.

He remained confident that the 16 mine employees and 13 contract miners had survived.

"This is a search and rescue operation, and we are going to bring these guys home," Knowles said.

The blast was most likely caused by coal gas igniting, Pike River Mine Ltd. chief executive Peter Whittall said.

Electricity in the mine went out shortly before the explosion and that failure may have caused ventilation problems and contributed to a buildup of gas. The power outage continued to frustrate efforts Saturday to pump in fresh air and make it safe for rescuers, though Whittall said air was flowing freely through a compressed air line damaged in the explosion.

"We have kept those compressors going and we are pumping fresh air into the mine somewhere. It is quite conceivable there is a large number of men sitting around the end of that open pipe waiting and wondering why we are taking our time getting to them," Whittall said.

A working phone line to the bottom of the mine, however, had rung unanswered.

The two dazed and slightly injured miners stumbled to the surface hours after the blast shot up the mine's 354-foot (108-meter) -long ventilation shaft. The men were taken to a hospital for treatment of minor injuries and were being interviewed to determine what happened. Whittall said one of two men had used the phone to contact the surface before walking out.

The explosion occurred about 3:45 p.m. Friday. Video from the scene showed blackened trees and light smoke billowing from the top of the rugged mountain where the mine is located, near Atarau on South Island. It is New Zealand's largest underground coal mine.

Families of the missing men gathered at a Red Cross hall in nearby Greymouth on Saturday, and were being briefed hourly on rescue efforts. Most have declined to talk to reporters, as have the two men who made it out of the mine.

"There is a great sense of anxiety and genuine fear, and I think that's only natural given the ... difficulty of the situation," Prime Minister John Key told reporters after visiting the families. "We reflected to them that they have to hang on to hope. As we saw in the case of Chilean mine, 33 miners did get out alive."

But unlike the accident in Chile, where 33 men were rescued from a gold and copper mine after being trapped a half mile (one kilometer) underground for 69 days, Pike River officials have to worry about the presence of methane, mine safety expert David Feickert said.

He added, however, that the Pike River mine has two exits, while the mine in Chile had only one access shaft that was blocked.

The coal seam at the mine is reached through a 1.4-mile (2.3-kilometer) horizontal tunnel into the mountain. The seam lies about 650 feet (200 meters) beneath the surface. According to the company's website, the vertical ventilation shaft rises 354 feet (108 meters) from the tunnel to the surface.

Whittall said the horizontal tunnel would make any rescue easier than a steep-angled shaft.

"We're not a deep-shafted mine so men and rescue teams can get in and out quite effectively, and they'll be able to explore the mine quite quickly," he said.

Each miner carried 30 minutes of oxygen, enough to reach oxygen stores in the mine that would allow them to survive for "several days," said Pike River chairman John Dow.

Australian and British citizens were among the missing men, and Australia sent a team of mine rescue experts to assist the operation.