Experts have said that further rockfall in the area cannot be ruled out after the rockslide early on Tuesday, NRK reports.
Resident Magnus Bjerve told the broadcaster he initially thought an avalanche had occurred.
“I heard the slide at around 7:30am, and thought maybe snow or ice had fallen down. When I went outside I saw the large rocks,” said Bjerve, who lives in one of the apartments in the affected building.
Police were informed of the incident by residents.
“Nobody was hurt by the rockslide. There was only material damage to the building entrance,” Oslo police response unit leader Steinar Bjerke told NRK.
The building, which contains several apartments, is located on Ribbunggata, a street directly underneath the steep Ekeberg area.
A safety net fastened to the back of the building was found to contain several rocks, despite being dislodged itself during the rockslide.
“Most of the rockslide was fortunately stopped by the safety net,” Bjerve said.
“We don't know when we'll be able to move back in,” the resident said, adding that the building's co-owners, including himself, shouldered initial responsibility for securing the area and clearing the debris, given the rockslide occurred on privately-owned land.
Photo: Terje Pedersen / NTB scanpix
The Norwegian Geotechnical Institute (NGI), which has investigated the area, said the rockslide was typical of the season.
“When it is spring and ice melts in the bedrock, it is often the case that previously unstable rocks become loose. We already know that this area is unstable, which is why it is secured with nets and pins, but that has not been good enough,” NGI geotechnician Arnstein Aarset told NRK.
NGI has requested immediate measures to secure the hillside.
"There are deep cracks in the structure that make the mountain unsafe," Aarset added.