A rock slide wrecked a six-story apartment building in a Norwegian coastal city early Wednesday and rescuers feared five missing people have been killed. Fifteen people were taken to a hospital, police said.

The search for survivors was hampered by two later rock slides that hit the crumpled building, partly built into a steep hillside in Aalesund, about 220 miles northwest of Oslo.

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The bottom floors of the building caved in just after 3:30 a.m. when the first slide slammed into the building.

"We first thought it was an earthquake," said Lars Aage Eldoey, who managed to escape with his wife from the top floor of the building. When he got out on the balcony he realized what had happened.

"There were enormous rocks — not just rocks — half the hill had slid down into the bottom floors," he told state broadcaster NRK.

The subsequent slides caused fires to flare up, and authorities evacuated neighboring buildings, rescuers said.

Smoke billowed from the twisted bottom floors of the collapsed building, with sagging balconies and a contorted glass entryway.

Rescuers said five people who lived in the building were unaccounted for and possibly buried by the debris inside.

"We fear that the missing people are dead," police rescue leader Kjell Kvenseth told the TV-2 network at the scene.

Fifteen people were taken to a hospital, two of them with moderate injuries, Aalesund police operations leader Magne Tjoennoey said.

A fire smoldered in the debris, and police feared that a 2.8 ton propane tank buried near the building could explode.

Tjoennoey said rescuers had not been able to enter the building, which was finished in 2003, to search for the five missing people.

"We have not been able to find out where they are," he said. "As time goes by, we increasingly fear that they are in the building."

A helicopter, rescuers and search dogs from around the region were called to the scene, including the Norwegian unit of the United Nations International Search and Rescue Advisory Group, he said.

"The bottom floors are collapsed. There is a big risk in going inside, and there is also the risk of fire," he said.