Chinese police have taken into custody four Taiwanese employees at Hon Hai Precision Industry Co., Apple Inc.’s main assembly partner, the latest in a spate of detentions that have rattled investor confidence in the country.

Taiwan's Mainland Affairs Council, in a statement to Reuters on Thursday, said the four employees had been detained in China's Zhengzhou, home to a major Foxconn plant assembling Apple's iPhones, on suspicion of the equivalent of "breach of trust".

Four Taiwanese employees at Chinese facilities that make products for Apple have been detained by local authorities.