The local police in Southwest China's Yunnan province are probing cases of eight missing young men, including one who managed to escape after he was kidnapped and sold to a brick factory as an unpaid laborer.

The eight men, aged from 12 to 24, went missing at different times over the past couple of years near a cold storage facility in a village of Jincheng township, which is located less than 40 kilometers away from Kunming, capital of Yunnan province.

Six of them went missing over the last year and most of the cases happened from 9:00 am to 11:00 am, according to a report of the Shanghai-based Oriental Morning Post.

The latest case happened on April 25, when 19-year-old Han Yao disappeared while walking across a small forest less than 100 square meters away from the storage space, said his father.

Han had just graduated from a local vocational school, and it was inconceivable that he would run away from the family, his father added.

Cai Yunwei, 17, disappeared at about 9:30 am on Feb 17 when he went to the toilet near the cold storage facility, said his mother Guan Lianmei.

His father said that he had just bought a pack of instant noodles before he went to the toilet and went missing.

Some locals reported seeing a gray van carrying men who tried to forcibly take passing teenagers inside, but police have not been able to verify these claims at this time.

Zhang Linhui, a middle-aged man who lived near the small forest with his wife, said that the number of missing teenagers in the area has increased since 2011.

The local police said they have received reports of seven cases and are investigating the cases, which have already caused panic among the locals.

Lei Yusheng, 24, a migrant worker in a wine company near the small forest, was forcibly taken into a yellow van on April 7 when he was walking to town for a haircut.

He was taken to a brick factory on April 8 to work without payment, where he had to work for 10 hours each day from 2 am to the noon. The factory was guarded by two men, and he finally managed to escape on April 25 while the guards were taking a break.

"There are two men in the van, both taller than 1.8 meters," he recalled. "The man who took me into the van looked to be 20 to 30 years old, and the driver seemed older."

Lei said that there was a knife of 50 cm in length under the driver's seat, and he had to obey their orders for fear of being injured.

He reported the case to the local police after he escaped, and the police said they have started investigating.