Police closed part of a motorway in Greater Manchester after items were thrown from a car they were chasing.
Officers started pursuing a grey Audi A4 after it rammed into a police car in Moorside Road, Kersal, at about 1330 BST, a police spokesman said.
They followed the Audi to the M61, at which point people inside started to throw items from the windows.
A rolling road block has been put in place from junctions two to six, so officers can recover the items.
The car was found abandoned in Hall Lane Grove, Hindley a short time later.
Officers are still trying to trace the driver.