Wellington - Flags on government buildings will fly at half-mast on Thursday in New Zealand as Prime Minister John Key expressed his condolences for the loss of 29 miners on Wednesday.
Speaking at a media conference in the capital Wellington, Key said a commission of inquiry into the incident should be launched early next week.
Key will also travel to South Island West Coast on Thursday to meet with families of the lost miners and the rescuers who tried to save them.
He said the rescuers had put in an "enormous effort" that could not go unmarked.
Key said the loss of the miners was a "national tragedy", adding: "We are a nation in mourning."
Speaking to those who had lost loved ones in the tragedy, Key said the entire country was standing "shoulder to shoulder" with them during this terrible time.
On behalf of the country, he sent a message of sympathy to all those who had suffered a loss, saying New Zealand was a small country where this type of tragedy affected so many.
Police Superintendent Gary Knowles, who headed the rescue operation, said the second explosion, at 2:37 pm on Wednesday, was so powerful that no one could have survived it.
"Unfortunately I have to inform the public of New Zealand at 2:37 pm today there was another massive explosion underground and based on that explosion no one would have survived," Knowles said.
"I was at the mine myself when it actually occurred and the blast was prolific, just as severe as the first blast (last Friday)," he added.
Knowles said he was with a rescue team when the blast happened and they were in agreement with him that the miners would have "perished".
Police said there is now no chance of the miners being alive and they are going into recovery mode.
Grey District Mayor Tony Kokshoorn, who was at the civic center when the news was broken to the families, said "this is the West Coast's darkest hour".
He said the news had been "sickening", and families were devastated. The families and communities of the dead miners have been changed forever by Wednesday's catastrophic blast, he said.
"This has got to be the darkest day for me, for Greymouth, for everywhere," he added.
He said families fell to the floor when they heard the news.
Pike River Coal mine chief executive Peter Whittall told a media conference that it was still unsafe for a recovery team to enter the mine.
Whittall said monitoring of gases through a bore hole prior to the explosion revealed methane concentrations of 95 percent.
Gas testing would continue, he said, because the mine remained as unsafe as before.
The 29 men have been missing since the first explosion last Friday. One of the 29 miners trapped underground was a South African. Other workers include 24 New Zealanders, two Australians and two British citizens.
