GUANGZHOU, May 31 (Xinhua) -- A total of 311 children have been rescued in a crackdown on child smuggling in south China's Guangdong Province over the past year, police authorities said Monday.

Police arrested 645 people in 276 child smuggling cases from April last year to May 25 this year, said Zhai Kaixia, deputy director of the criminal investigation department under the provincial public security department.

The nationwide DNA database designed to tracing missing children and cash rewards for information were instrumental in the crackdown, Zhai said.

Zhai said the DNA database had helped reunite a boy in Shantou City with his parents in Kunming, capital of southwestern Yunnan Province, 11 years after he was sold to a man surnamed Chen for 13,800 yuan (2,020 U.S. dollars).

The reward for tip-offs leading to the arrest of a suspect is 5,000 yuan and 10,000 yuan for information leading to the rescue of a child. The reward for a tip-off was capped at 50,000 yuan, he said.