Four unfurnished villas that sit on top of a shopping mall in Zhuzhou, Hunan province, have led to questions about their safety, but city planners said on Wednesday the structures were built legally and with the required documentation.

The buildings, which have electricity and water pipes already installed, will be offices for the shopping mall developer's 160 real estate management employees, said Li Li from the Zhuzhou city planning bureau.

The bureau conducted an on-site investigation after media reports voiced concern over alleged safety hazards and the legal status of the four buildings.

The developer, Zhuzhou Jiutian Real Estate, used modern designs and landscape decorations to make the buildings look like villas, but never intended to sell them, Li said.

The construction of the shopping mall — including the rooftop buildings in the mall’s four corners — obtained authorities' approval, he said.

The Zhuzhou government has made steady investments to build a green city after it was named one of 34 national-level garden cities in 2008.

Other cities are making similar efforts. Beijing introduced a new rule in 2011 that requires green rooftops with living vegetation on buildings that have fewer than 12 floors, are shorter than 45 meters and were built within the last 20 years.

Lu Bin, a landscape designer in Beijing, said he had never seen any building in Beijing with rooftop houses, though some have pavilions on the top.

To avoid safety hazards, landscape designers usually use grass and low-growing plants for rooftop greening, he said.

Rooftop villas have surfaced as an issue before.

In October, residents in a 12-story building in Wuhan, Hubei province, complained of serious leaking from a rusted pipe on the top floor. The pipe was unreachable because it was underneath one of the four villas on the roof.

The developer of the residential building completed the building and villas in 1999 and later sold the villas. Some people still live on the roof, said a woman surnamed Liu who works for the property management office. She declined to give her full name.

The entire property was built with authorities' approval. The four villas have the required certificates of house ownership and the right to use the land, Liu said.

The city planning bureau in Wuhan investigated the case after receiving complaints from residents.

The leaks were repaired. And residents have withdrawn their complaints, said Tang Jun from the bureau’s law enforcement team.

Contact the writers at liyao@chinadaily.com.cn and fengzhiwei@chinadaily.com.cn