The remaining 131 people held for clinical observation of the bird flu have been released, health officials confirmed on Wednesday in Anhui Province.

They had all been allowed to leave by 12:00 a.m. Monday, as no abnormal symptoms were reported during the observation. Their temperatures were taken and reported to the provincial disease control center everyday, said the local health department.

Another 37 people who were proven to have close contacts with dead chickens were released from clinical observation on July 17.

Despite the end of observation, local health departments will maintain a high level of vigilance. They will continue the daily reporting system and observe patients with fever arising from unknown reasons.

Early in July a chicken death was confirmed to be caused by H5N1, a highly pathogenic bird flu virus, at a poultry farm of the Juchao District, Chaohu City of Anhui Province. It was the first case after an earlier outbreak between January and March, 2004.

Following the death, the local government immediately isolated the area around the chicken farm in line with China's Law on Animal Epidemic Prevention. Not a single case of the bird flu has been reported since that report.