GREYMOUTH, New Zealand — A massive explosion deep inside a New Zealand coal mine today erased hopes of rescuing 29 miners caught underground by a similar blast five days ago. The prime minister declared it a national tragedy.

Even if any of the missing men had survived the initial explosion Friday at the Pike River Mine, police said none could have lived through the second. Both blasts were believed caused by explosive, toxic gases swirling in the tunnels dug up to 1½ miles into a mountain that had also prevented rescuers from entering the mine to search for the missing.

“There was another massive explosion underground, and based on that explosion no one would have survived,” said police superintendent Gary Knowles, in charge of the rescue operation. “The blast was prolific, just as severe as the first blast.”

It was one of New Zealand's worst mining disasters. The country's industry is relatively small compared to other nations and considered generally safe, with 210 deaths in 114 years after the most recent tragedy.

PHNOM PENH, Cambodia — A swaying bridge loaded with thousands of people sparked mass panic and set off a raging stampede that killed more than 350 people in Cambodia’s capital, according to a government investigation.Crowds celebrating a water festival had flocked to an island for a free concert Monday and spilled onto a bridge to the mainland before the panic took hold. Bayon TV, which serves as a mouthpiece for the government, reported today that a committee found many people on the span were from the countryside and unaware it was normal for a suspension bridge to sway. In their fear it was collapsing, they tried to run off.