GREENFIELD, Wis. (AP) — A driver being pursued by police died when his vehicle struck a tree in Milwaukee.

Greenfield police say an officer began chasing the 25-year-old West Allis man shortly before midnight Thursday after attempting to stop him for speeding.

Police say the Greenfield officer used an unexplained "intervention technique" just before the vehicle crashed into the tree.

The driver has not been identified. The officer has been placed on administrative leave.