Updated

Shares of supply chain provider Plexus Corp. plunged Wednesday after it announced that it had been dropped as a supplier to Juniper Networks Inc., a data network equipment maker.

Shares were down $7.70, or 27.6 percent, at $20.26 in afternoon trading Wednesday after falling as low as $19.63 earlier in the day, its lowest level since July 2009.

CEO Dean Foate said the company was informed of the decision on Monday, calling it "very surprising news."

"Plexus has been an important strategic supplier to Juniper for more than a decade. While this is a significant event for us in the near term, our new business wins of $956 million during fiscal 2012, including in the networking/communications sector, provides us continued optimism in our strategy," he said in a statement.

Plexus said in a news release that the timing of the separation of Plexus as a supplier to Juniper wasn't known but is expected to be by the end of its fiscal year.

Plexus is based in Neenah, Wis. Juniper is based in Sunnyvale, Calif.