Construction on the world's highest building in central China hasn't started, a year behind schedule, while its construction site has been used to grow crops, the National Business Daily said.

A guard at the construction site of Sky City, a projected 838-meter building in the capital city of Hunan, said work had been halted since last June, days after a ground-breaking ceremony.

Most of the land has been used to grow crops such as watermelon and corn by local farmers. A man said no one had prevented him.

The Changsha-based construction company Broad Group had expected to finish the project in April 2014, with a building time of just 10 months. But it turns out that they were too optimistic.

She Haoyu, head of the local management committee, said the mega building needs special approval from the country's ultra-high building committee, which the group has received. The company is now designing firefighting facilities to pass safety inspections, he said.

Construction cannot begin without all the necessary permits, She said, adding that the construction of lower backing buildings can start, as long as they get permits from local governments.

Wei Chunyu, head of the Architecture School at Hunan University, said he considers the firefighting facilities a big issue and "it is quite difficult to design," he said.

The Broad Group responded that a firefighting research institute in Tianjin under the Ministry of Public Security has shouldered the task. It also revealed that the steel they used can resist fire for three hours.

Experts believe that the long delay shows the group failed safety inspections before.

The group has added 5 billion yuan ($805 million) to the project, for a total of 9 billion yuan ($1.45 billion), while the group's revenue in 2012 was around 6 billion ($967 million) yuan.

A spokeswoman for Sky City declined to comment and said the company will release some information in October.

The 208-story tower is expected to be 10 meters taller than the current record holder, Burj Khalifa in Dubai.