A massive unauthorized basement in an old hutong neighborhood in Beijing is now being filled, authorities said on Friday.

The 318-square-meter basement in Qinglong Hutong, Dongcheng District, was reported by local residents and confirmed by local police, Nie Jia, a law enforcement officer said. The basement is about 1.6 meters to 2 meters deep.

Work to fill the basement started on Wednesday and is about halfway done, he said.

Earlier this year, radar was used to detect unauthorized basements throughout Beijing as the city seeks to eliminate the potentially dangerous practice. The crackdown comes after a lawmaker built a basement in his courtyard that caused neighboring houses to collapse.

Li Baojun, a lawmaker from east China's Xuzhou City, Jiangsu province, built an 18-meter-deep basement in his courtyard in Xicheng District without permission, which caved in and caused the road and surrounding buildings to collapse on Jan. 24.

The incident revealed rampant illegal underground construction and caused concern across the country.