A pod of about 40 beached pilot whales re-stranded themselves in New Zealand Tuesday after volunteers worked for hours to get them back into the sea, officials said. The pod was part of a larger group of about 100 pilot whales which stranded at Golden Bay on the South Island on Monday, the Department of Conservation (DOC) said. DOC spokesman Nigel Mountford said 34 of the original pod were confirmed dead and 26 were successfully refloated late Monday and had swum offshore. He said hopes were fading for the remaining pilot whales, which swam back to shore after volunteers manoeuvred them into the water early Tuesday afternoon. \"It\'s disappointing, they just came back on shore,\" he said. \"They\'ll have to take their chances at high tide overnight. It\'s too dangerous for our volunteers to stay through the night, we\'re working right at the edge of our capability.\" Mass strandings are common on the New Zealand coast and more than 50 pilot whales have died in two separate beachings in the same area in the past two months. Pilot whales, which are members of the dolphin family and grow up to six metres (20 feet) long, are a common sight in New Zealand waters. Scientists are unsure why pilot whales beach themselves, although they speculate it may occur when their sonar becomes scrambled in shallow water or when a sick member of the pod heads for shore and others follow.