GREYMOUTH, New Zealand, (AFP) - All 29 men missing in a New Zealand coal mine have died after a powerful second blast tore through the pit, authorities said Wednesday, plunging the country into mourning. Police said there was now no chance of finding anyone alive, confirming the countrys worst mining accident in nearly a century. Prime Minister John Key called it a national tragedy and said flags would fly at half-mast. Where this morning we held on to hope, we must now make way for sorrow, Key said. Today, all New Zealanders grieve for these men. We are a nation in mourning. Police Superintendent Gary Knowles, who led stuttering rescue efforts, said he was at the mountainside Pike River mine when the sickening second explosion hit at 2:37 pm (0137 GMT), five days after Fridays initial blast. There was another explosion at the mine. It was extremely severe, he said. Based on expert evidence I have been given... it is our belief that no one has survived and everyone has perished. The news prompted anguish and anger among relatives, who had suffered an agonising wait for a rescue that never came as toxic gases stopped emergency teams from entering the mine in New Zealands South Island. In the grief-stricken town of Greymouth, home to many of the miners, builder Mike Curtis said locals were united in believing that rescuers should have gone in straight away - all the old-timers knew that. The victims of the blasts ranged from a 17-year-old on his first shift to a 62-year-old veteran, and include two Australians, two Britons and a South African. District mayor Tony Kokshoorn said the incident was the darkest hour of New Zealands rugged West Coast region, a centre of the countrys burgeoning mining industry based on exports to Asia. The mine is a new facility that sent its first shipment of hard coking coal for making steel to India only this year. Its unbelievable. It doesnt get worse than this, Kokshoorn said, adding that devastated relatives were questioning why a rescue was not attempted sooner. They just sobbed openly, just fell to the floor. There were people just shouting out, anger, he said. The cause (of the second explosion) was the build-up over the last five days of the gases again and they noticed this morning. A lethal mixture ignited the entire mine. Stop-start rescue efforts had earlier inched forward when a borehole into the mine finally broke through, but found only a toxic cocktail of dangerous gases with little oxygen. A remote-controlled robot - the second such device after a first one broke down - also travelled about a kilometre (two-thirds of mile) into the mine and found the helmet of one of the only two survivors, its headlight still on. But rescue efforts were dramatically ended when the second blast ripped through the gas-filled network of tunnels. Energy Minister Gerry Brownlee said efforts would be made to recover the bodies of those killed. He said a series of inquiries aimed at finding out the cause of the disaster and preventing any repeat would be carried out.