Taiwanese prosecutors raided a plant belonging to Unimicron, one of the world's biggest chip substrate makers, which is bad news for a company sitting at a key point in the AI chip supply chain.

• Taoyuan prosecutors confirmed a search of Unimicron's Hejiang plant in Zhongli was nearly finished.
• More people connected to the case may be taken in for questioning.
• No reason for the raid has been given yet; details are due in a later statement.
• Unimicron makes the boards that carry advanced chips, so any disruption ripples out to chipmakers.

Outlook: Prosecutors are expected to explain the case shortly, and investors will watch for any hit to Unimicron's output or management.