German broadcaster ARD says one of its crews was attacked and detained for nine hours while filming at a Chinese factory for a story about pollution.

Correspondent Christine Aldehardt said a SWAT team rescued them from the factory cafeteria Saturday as workers outside chanted "death to the foreign spies."

She said security guards detained the four-person crew as they filmed outside the Do-Fluoride factory, which makes industrial chemicals. Their driver and a local activist were held, too.

At one point, workers broke into the cafeteria and seized the crew's tape after accusing them of filming commercial secrets. People reached at the factory who wouldn't give their names confirmed the crew had been there and repeated the spying claims.

The factory is two hours outside Zhengzhou, the capital of Henan province.