Miners' Deaths A National Tragedy, New Zealand Prime Minister Says

(CNN) All 29 miners trapped underground following an explosion last week in a New Zealand mine are dead, the official in charge of the rescue attempt said Wednesday.

"There was another massive explosion underground, and based on that explosion, no one survived," Gary Knowles, superintendent of Tasman Police Command, told reporters. "We're now going to recovery mode."

Knowles said he was at the mine when the second explosion occurred on Wednesday afternoon.

"The blast was horrific -- just as severe as the first blast," he said. Knowles said he did not know and would not speculate on the cause of the blast.

During a news conference Wednesday, New Zealand Prime Minister John Key said like many in his country, he had hoped for a miracle.

"This is a national tragedy," Key said, "a tragedy for the men's families, for their work mates and friends, for their community and our nation.

"New Zealand is a small country -- a country where we are our brother's keeper. So to lose this many brothers at once strikes an agonizing blow."

Key extended condolences to the families of the miners.

"To all those who lost their loved one in the Pike River mine, let me say this: New Zealand stands shoulder to shoulder with you. Though we cannot possibly feel this pain as you do, we have you in our hearts and our thoughts."

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.