Law enforcement officials check the basement illegally dug under houses in Shaluo hutong, Dongcheng District in Beijing, on Nov 19, 2015. [Photo/IC]

A basement illegally dug under a house in Beijing was exposed Friday, less than one year after excavation in a courtyard in the city's Xicheng District led to a road cave-in and the collapse of neighborhood houses.

The illegal basement, the largest found in Beijing, was built under two adjacent houses in Shaluo Hutong, Dongcheng District. It is spread out over about 700 square meters spread across three floors underground and the deepest point is 10 meters, according to a preliminary measurement, said Yan Jianheng, director of demolition office dealing with illegal construction in Dongcheng District.

The property owner, surnamed Li, bought the houses in 2008 and registered them under his and his son's names, law enforcement officials said.

The owner, who is in his 50s, operates a car rental company, and planned to use the basement as a garage, according to people familiar with the matter. When the digging work was finished, the basement was to have accomodated 100 cars.

He hired part-time workers for the construction after designing the underground parking lot. To avoid notice, they used shovels instead of large machines and worked from midnight to early morning.

Officials from Beijing Municipal Commission of Housing and Urban-Rural Development said they have invited a third-party institution to evaluate the basement. If it endangers public security, the case will be handed over to the police.

Li will face an administrative penalty, with a maximum fine of 10 percent of the overall construction costs.