Hon Hai Precision Industry Co. fell its most in more than three months after Beijing launched a series of investigations into its operations in China, targeting a key Apple Inc. supplier and one of the country’s largest employers.

The Taiwanese firm, which makes the majority of the world’s iPhones from its factories in central and southern China, slid 3.4% in early trading Monday.

Foxconn is Apple’s most important assembly partner, cranking out millions of iPhones a year from a giant complex in Zhengzhou known as iPhone City. Tax authorities are now conducting checks on its subsidiaries in Guangdong and Jiangsu provinces, the state-run Global Times reported Sunday, citing unidentified people with knowledge of the matter. Natural resources officials are also looking into the company’s use of land in Henan and Hubei provinces, according to the report.

No further details of the investigations were provided. Hon Hai said it will collaborate with Chinese authorities on the probes, but didn’t offer specifics in a filing with Taiwan’s stock exchange.

Read More: Apple Supplier Foxconn Working With China on Some Probes