Seven Chinese students who tested positive for hepatitis B sued their city's education bureau after they were forced to drop out of school, their lawyer said Monday.

Last month, 19 students from several boarding schools in the western city of Urumqi were forced to leave because authorities "believed they were infectious and should drop out," said attorney Zhang Yuanxin.

Their parents believed the decision had no legal basis, and Zhang sued on behalf of seven of students from the Urumqi No. 15 Middle School, he said in a telephone interview on Monday.

"Although the students tested positive for hepatitis B, their livers were functioning normally," Zhang said. "They had medical proof from doctors showing it was not a problem for them to live with other students."

Hepatitis B is spread by contact with infected blood or through sex. It can survive briefly outside the human body. The Chinese government says the country has 120 million people who suffer chronically from the virus.

According to regulations of the Xinjiang bureau of education and health, students who carry the hepatitis B virus are allowed to enroll in schools as long as their liver functions are normal, Zhang said.

A woman who answered the telephone at the education bureau Monday evening said no one was available to answer questions.

The Urumqi Tianshan District People's Court accepted the case last week and said Monday that a date for the hearing had not been decided.