After four years performing in streets around the country with an illegal circus, 13-year-old Zhang Xinkai has been reunited with his family, thanks to police in Shanghai.

Zhang Xinkai, 13, who was rescued from a touring circus, gets a hug from his grandmother at a police station in this photo released yesterday by police in Shanghai's Fengxian District where he was found on the street.

Zhang's father and grandmother came to the city earlier this week to take the boy home to Xuzhou, a small city on the north tip of Shanghai's neighboring Jiangsu Province, police said yesterday.

Tightly clutching her long-missing grandson by the arm, the grandmother knelt down in front of city police officers to express her thanks.

"Thank you for all you have done for me," said the boy in a letter to police officer Yang Dongchun, who found and rescued him in suburban Fengxian District.

Two organizers of the circus have been detained, police said.

On July 22, Yang, who was on duty in Qixian Town in Fengxian, saw the boy performing with a snake as part of a circus act on the street. "He was the only one whose clothes were in shreds and tatters," said Yang. "He was obviously undernourished."