New Zealand Prime Minister John Key has declared a national state of emergency as the death toll from Tuesday's earthquake in Christchurch rose to 75. Police have said there is "incredible carnage right throughout the city", with "bodies littering the streets". More than 300 people are still missing. Forty-eight were pulled out from collapsed buildings alive overnight. The search has now been abandoned at one office block, but elsewhere a woman was rescued after more than 24 hours. "The situation is that we don't believe this site is now survivable," said police area commander Inspector Dave Lawry near the remains of the Canterbury Television building. "It was a hard choice and my heart goes out to all the families." He said rescuers now needed to concentrate their resources elsewhere in areas where survivors were more likely to be found.