HONG KONG, April 29 (Kyodo) — Some 1,000 people in eastern China's Zhejiang Province have been treated for gas poisoning in the wake of an explosion Tuesday night at a pharmaceutical plant, a human rights watchdog said Thursday.

The explosion at the plant run by Apeloa Tospo Pharmaceutical Co. plant in Hengdian town caused poisonous gas such as sulfur dioxide to leak, sickening people living in the area, the Hong Kong-based Information Center for Human Rights and Democracy said.

About 1,000 people suffering symptoms like nausea and vomiting since the explosion have been treated at two hospitals, it said, citing hospital sources.

The center also said plain-clothed security officers beat up a reporter from a local TV station and confiscated his video camera as he was covering the incident Wednesday.

China's state-run Xinhua News Agency has reported only about a fire occurring at the site that sickened a few people.

Apeloa Topso, producing antibiotics and medical chemicals, was founded in 1990 as a subsidiary of Hengdian Group, according to the company website.

The plant was reportedly fined 2.2 million yuan ($321,000) in January for illegal dumping of poisonous chemicals in the neighboring Anhui Province.

The company and the provincial government could not be reached for comments.

Hengdian is known throughout China as the major shooting site for Chinese films.