XI'AN, Feb. 10 -- A four-story office complex built inside a renovated section of the ancient city wall in China's northwestern city of Xi'an has sparked preservation concerns.

An article posted on the provincial government publicity department's website claimed that a section of the ancient wall had been hollowed out to make way for the office complex.

The story drew much criticism, especially as local authorities had been working toward securing world cultural heritage status for the wall.

The modern office complex features conference rooms, offices, a dining hall and a rehearsal hall. It is used by the administration's committee for the Xi'an City Wall Scenic Area.

The report quoted a city preservation expert, who said the construction work had damaged the cultural relic.

However, officials from the committee were of a different opinion.

Since the early 1980s, the Xi'an government has initiated restoration projects for the 13.74-km-long ancient city wall, as it has been seriously damaged throughout its 600-year history. As a result many of the wall's multiple breaches, or hollow caves, have been filled in.

In 1993, a 100 meter long reinforced concrete wall was built to fill the breach at Chaoyang Gate, said Li Jujian, an official with the administration committee. The structure was in harmony with the ancient wall.

Unlike the original city wall, which was built with soil and bricks, the newly added section was cavernous. Thus, the space was used for the office complex.

Xi'an rural and urban housing commission staff began to use the complex in 1993 and in 2014, after it was renovated, the scenic area committee moved in.

However, the complex has no natural ventilation or sunlight, said Li, making it an unsuitable working environment.

"If there were other choices, we would move out," said Li.

Xi'an, an ancient city with a history spanning more than 3,000 years, was the seat of 13 ancient dynasties. The city wall, built in the early Ming Dynasty (1368-1644), is one of the best protected ancient city walls in China. It is on the country's protection list.

Duan Qingbo, a cultural heritage expert at Xi'an Northwest University, said the office complex could not have damaged the wall as it was a bi-product of the 1990s protection and restoration project.

But the structure still had an impact on the relic, he said. Cultural heritage authorities should investigate the problem and provide protection solutions, said Duan.

If the interior space can be filled up, or used for exhibitions, this would better suit the style of the city wall, he suggested.