ZHENGZHOU - Most of the 30 enslaved and abused workers rescued from illegal brick kilns in Central China's Henan province have been unable to give their personal details to police due to their mental illness, public security officials said on Tuesday.

Henan police liberated the victims, some of who have worked without pay for more than seven years, in four counties and cities on Sunday.

However, Liu Weiming, deputy director of publicity in Zhumadian, where 17 mentally ill laborers were rescued from two brick kilns, said the workers are unable to reveal their identities and have been sent to a nearby relief center.

"Some of them can't even speak a whole sentence, and they don't act like normal people," Liu said. "Most are staying at a relief station because they can't remember where they are from."

Sun Mengyang, a publicity official in Dengfeng, where five disabled workers were rescued, said police there have experienced similar problems.

He added that authorities have called for further investigations to make sure all illegal brick kilns are closed.

According to a report by the TV channel that exposed the scandal, City Report in Zhengzhou, the victims were largely abducted from streets and railway stations and then sold to bosses at brick kilns for 300 yuan to 500 yuan ($45 to $80).

Bai Shasha, 23, a mentally disabled worker from Luoyang city who was rescued by police in July, says several people with knives abducted him in March after he and his father got lost in the suburb.

He told City Report he was taken to a brick kiln, where he was regularly beaten with whips and bricks.

His bosses ordered them to work all day without a rest, and at night they slept in cramped and smelly conditions, according to the report.

Publicity official Liu said authorities in Zhumadian have detained two bosses and a supervisor.

Meanwhile, a police officer was quoted by Southern Metropolis Daily on Monday as saying that one supervisor accused of beating the workers with whips is just 14 years old.

Calls to Henan public security department went unanswered on Tuesday.

In December 2010, Zeng Lingquan, a member of the Chinese People's Political Consultative Conference, and his wife Li Shuqiong were arrested for selling at least 130 mentally ill people to coal mines, chemical factories and construction sites nationwide, from which the couple made more than 3 million yuan, Oriental Morning Post reported.

Yang Hanping, vice-president of the China Institute of Industrial Relations, said on Tuesday that more attention should be paid to mentally disabled workers.

"They are a vulnerable group who might be easily cheated," Yang said. "Apart from the public security department, social organizations such as workers' unions and the Disabled Persons' Federation should do more to protect the rights of mentally disabled workers."

Liu Xiangrui and Jin Huiyu contributed to this story.