NANNING, Jan. 31 (Xinhua) -- More than 220 kg of methamphetamine, 650 kg of semi-finished drugs, and more than 14,300 kg of drug-making materials have been seized by police in the city of Laibin in southwest China's Guangxi Zhuang Autonomous Region.

Thirteen suspects have been detained, a meth lab has been shut down, and five vehicles, 70,000 yuan in cash and a grenade have been confiscated, local police said Wednesday.

The drug production gang caught the attention of police in November last year. After a month of investigation, police found that a father and son, surnamed Lan, had been making drugs in a forest in Jinxiu County and selling them outside the city.

Eight suspects were caught on Jan. 17, another three on Jan. 19, and the remaining two on Jan. 24.

Police also found two rented warehouses in Mengshan County, which the suspects had used to store drugs and drug-making materials.

The case is under further investigation.