BEIJING - Nearly 1,000 people have been arrested in a nationwide crackdown on the manufacture and sales of a banned and hazardous food additive in the past six months.

Police seized 2.5 tons of clenbuterol, a toxic chemical that is illegally used in animal feed to make pigs leaner, and six underground laboratories were shut down during the crackdown, which broke criminal rings in many cities, including Chengdu, capital of Sichuan province, and Wuhan, capital of Hubei province.

In all, at least 989 people have been detained for being involved in manufacturing, storing and selling the additive, including those in a criminal ring that was involved in the manufacture and sales of the chemical in 63 cities, according to a notice on the website of the Ministry of Public Security on Monday.

Despite the success of the crackdown, the ministry said it will continue to motivate all its branches, especially police substations at the grassroots level, to monitor any resurgence in the production and sales of clenbuterol in their duty areas, and share information with each other to promote early detection and investigation.

The police authority also wants the public to join the battle against illegal additives.

"We hope people can report such criminal activities to us actively," the ministry said in its online statement.

The ministry said the clenbuterol campaign was part of an attempt to curb "the momentum of criminal activities" and to safeguard people's food safety.

"The abuse of food additives remains one of the noticeable problems of food security," Li Yuanping, spokesman of the General Administration of Quality Supervision, Inspection and Quarantine, told a news conference on Monday.