LANZHOU - Seven people have been arrested over a scandal in which school children were forced to donate blood to a company in northwest China's Gansu province, police said Friday.

The suspects include Huang, deputy chief of a blood center run by Lanzhou Institute of Biological Products in the city of Wuwei, and six unemployed men. The company is one of China's largest producer of blood products.

Huang told police he was under pressure to find more donors towards the end of last year, so he asked a friend, Zhang, for help.

Huang said he offered 50 yuan (about 8 US dollars) in cash to first-time donors at the center.

Enlivened by the prospects of the reward, Zhang called together some friends who took primary and secondary school students to the center by force and pocketed the money themselves, according to an unnamed official with the public security bureau in Liangzhou District of Wuwei.

At least eight students aged from 10 to 16, were forced to donate blood at least once a month for seven months. Each time 600 cubic centimeters of blood was taken, three times the average amount for voluntary donors, the official said.

The gang earned an illegal income of 6,250 yuan.

The suspects always presented false ID cards at the center, pretending the donors were adults, he said.

The children were beaten if they did not cooperate and the scam was uncovered when one boy sought his parents' help after being beaten. His parents said he looked sick and pale.

In China, the legal age for blood donation is from 18 to 55. Blood centers are required to double-check the donor's identity before taking blood.

The case is under further investigation.