CHRISTCHURCH, New Zealand (CBS) -- Office workers trapped under their collapsed buildings sent messages to the outside as rescuers with dogs scrambled to save them and dozens of others following a powerful earthquake that killed at least 65 in one of New Zealand's largest cities.
At least 100 people were reportedly missing and believed buried. Search teams assisted by floodlights and earth movers worked through dawn Wednesday, trying to dig through crumbled concrete, twisted metal and huge mounds of brick. At least eight buildings in the business district collapsed. The spire of the iconic stone Christchurch Cathedral toppled into a central city square.
Medical workers brought the injured to a triage center set up in a park in central Christchurch, while military units patrolled near-empty streets disfigured by the huge cracks and canyons created in Tuesday's 6.3-magnitude quake, the second powerful temblor to hit Christchurch in five months.
The quake flattened tall buildings and sent chunks of concrete and bricks hurtling onto cars, buses and pedestrians below. Web designer Nathaniel Boehm was outside on his lunch break when the quake struck just before 1 p.m. He saw the eaves of buildings cascade onto the street, burying people below.
Others tried to claw their way in, but he didn't see anyone come out.
"People were covered in rubble, covered in several tons of concrete," he said. "It was horrific."
It even shook off a massive chunk of ice from New Zealand's biggest glacier some 120 miles east of Christchurch.
Thousands of people in the city moved into temporary shelters at schools and community halls. Others, including tourists who had abandoned their hotels, huddled in hastily pitched tents and under plastic sheeting as drizzling rain fell, while the Red Cross tried to find them accommodation.
Christchurch Mayor Bob Parker said it was impossible to say how many were still trapped in the rubble citywide, but it was estimated to be more than 100. He added that 200 workers skilled in rescues would search through the night.
Some who were trapped were able to call out using their mobile phones, reaching family, officials and media.
"I rang my kids to say goodbye," said Ann Voss, interviewed by TV3 from underneath her desk where she was trapped in a collapsed office building. "It was absolutely horrible. My daughter was crying and I was crying because I honestly thought that was it. You know, you want to tell them you love them don't you?"
She said she could hear other people still alive in the building and had called out to them and communicated by knocking on rubble.
"I'm not going to give up," she said. "I'm going to stay awake now. They better come and get me."
In the immediate aftermath, dazed, screaming and crying residents wandered the streets as sirens and car alarms blared. With ambulance services overwhelmed, some victims were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.
"It is just a scene of utter devastation," Prime Minister John Key said after rushing to the city within hours of the quake. He said the death toll was 65 and may rise. "We may well be witnessing New Zealand's darkest day."
A search-and-rescue team was being flown in from Australia, and the United States also dispatched a team to help.
A U.S. delegation of 43 government, business and community leaders was in Christchurch on Tuesday for a United States New Zealand Partnership Forum meeting. All were safe, the State Department said. Nine U.S. congressmen attending the meeting were reported to have left the city before the quake struck.
A more powerful 7.1 magnitude earthquake hit Christchurch, a city of 350,000, on Sept. 4, but caused no deaths. The latest one may have been deadlier because it was closer to where people live and work, centered 3 miles from the city, according to the U.S. Geological Survey. It also may not have been as deep underground.