(CNN) -- Authorities listed the nationalities Saturday of the 29 miners trapped in a New Zealand coal mine and said gas levels inside are still too high to attempt a rescue.
Most of the miners are New Zealanders, but there are also two Australians, two Britons, and one South African, New Zealand Police said.
Air samples taken late Saturday afternoon indicated the gas levels inside the Pike River mine were still high, making the risk for rescuers too great, said Gary Knowles, superintendent of the Tasman Police District, who is heading the rescue effort.
"Further samples will be taken in the morning, when the risks will be reassessed," he said. "It is a very complex situation and there are numerous risks we have to consider. We will continue to work through the night, and constantly reassess the situation."
An explosion rocked the mine, on New Zealand's west coast between Greymouth and Reefton, around 4 p.m. Friday (10 p.m. ET Thursday). Two men walked out with minor injuries, but their colleagues -- ages 17 to 62 -- were trapped as far as 2.2 kilometers (1.4 miles) from the tunnel's opening and have not been heard from since.
"Everyone here is totally focused on getting these men out and returning them to their families," Knowles said.
The rescuers are miners themselves, and are ready to go in as soon as it is safe to do so, he said.
The miners' relatives are away from the mine site, near the town of Atarau about 90 miles northwest of Christchurch, because "it doesn't add any value to the rescue operation and it doesn't add value to them, either" to be nearby Pike River Coal Chief Executive Peter Whittall said Saturday.
"There's 29 men down there. And there's 29 families. And there's 29 different sets of circumstances," said Whittall. "And all of them are dealing with it in their own way."
British Foreign Secretary William Hague said his thoughts are with the missing miners and their families and friends.
The British High Commission in Wellington is monitoring the situation closely, he said, and has been in contact with the British men's families.
The two survivors, one of whom has a brother trapped underground and whose father is the mine's safety manager, spent Friday night in a local hospital with moderate blast injuries before being released Saturday. They both have talked to authorities, who still don't know what caused the explosion or the current condition of the mine.
There are drinking water sources underground, said Whittall, and the workers likely brought some food with them. Although no contact has been made, officials are hopeful the trapped men found refuge near a ventilation shaft and might be getting fresh air from a broken compressor pipe.
The situation in New Zealand is different than the one in Chile, where rescuers last month successfully freed 33 men stuck for 69 days underground in a copper and gold mine.
There are two routes out of the mine, Whittall said. Unlike the Chilean mine, the shafts in the Pike River mine run horizontally into the hill, not vertically into the ground.
"This is not Chile. It's a whole different type of mine," said Knowles.
Still, like in Chile, government and rescue authorities said they've been getting offers of help from around the region and the world. Gas testing equipment has been flown in from Australia to help with the rescue operation, with engineering and health experts ready to assist.
A Facebook page devoted to the rescue effort had attracted more than 9,500 supporters by Saturday afternoon from people wishing the miners well, offering prayers and asking for information.
New Zealand Prime Minister John Key, who spoke briefly at the end of Saturday's news conference, said he has received offers of help from many groups and people, including an e-mail from Prince William saying his heart went out to the miners.
"From the government's perspective, we're doing everything we can to make sure these 29 brave men are taken out of the mine," said Key. "It's a difficult time for everyone."
