(CNN) -- As New Zealand observed a day of mourning Thursday for the 29 miners killed in an underground explosion, the government began investigating the cause of the blast.
"The government is absolutely committed to running a commission of inquiry that will leave no stone unturned to ensure that they get the answers to why the miners don't come home," said New Zealand Prime Minister John Key. "I think for the family, they have now accepted that their loved ones have gone, but they want answers."
The board of the company that operated the Pike River coal mine announced it was donating $500,000 (U.S. $379,800) to a fund to support the families and communities of the 29 men. New Zealand Oil & Gas Limited matched that amount, Pike River said, and it invited the public to contribute.
The first explosion at the mine, on New Zealand's South Island, happened last Friday. Authorities repeatedly said dangerous gas levels in the mine were too high for rescuers to enter, and two camera-bearing robots failed to find the men.
A second blast just as severe as the first happened Wednesday, eliminating the chance that anyone survived, said Gary Knowles, superintendent of Tasman Police command.
Thursday, Deputy Prime Minister Bill English said Parliament extended its sympathies and support to the victims' families and friends.
"It is important in particular that the children who have lost their fathers will remember them with pride and know that their loss was felt by a nation," English said.
The next step, English said, is to make the mine as safe as possible so the men's bodies can be recovered.
Acknowledging the anger and questions of the relatives, he said the government would give details of the commission of inquiry Monday.
"The scale and horror of this tragedy has dragged us all to the entrance of the Pike River mine and today we stand there together with the families and the West Coast community contemplating what might have happened in the darkness," English said. "Who among us did not hope that the qualities of these men, which we regard as the best of our own qualities, would triumph over the odds and lead them into the light?"
The inquiry will seek to find out what led to the accident, whether it could have been prevented, and what can be done to prevent a similar accident in the future, said Lesley Haines of the Department of Labour, which will be in charge of the commission.
During the rescue attempt, air released from drilling into the mine contained high levels of carbon monoxide and methane but little oxygen, according to police officials.
The chief executive of Pike River Coal, Peter Whittall, told reporters Wednesday he did not know where either of the blasts occurred in the mine, but said "the mine would have been filling up with gas. It would have already had gas in it."
The missing men, between the ages of 17 and 62, were believed to have been spread throughout the mine, with perhaps half trapped in one area, he said.
One of the robots that went in found a worker's helmet with its light still on that police said was dropped by one of the two miners who escaped the original explosion. Another robot reached a "fresh air base" and found nobody there, Whittall said.