Two kittens were killed after being dumped on Penryn bypass and struck by other vehicles this morning.
Police are investigating reports that someone dumped the young cats out of a moving car.
Someone reported spotting an arm come out of the passenger window of a red VW Golf on the bypass at about 9.15am and drop two objects.
A police spokesman said: "The witness stopped when he realised it was in fact two kittens and tried to catch them, but was unable to and they were run over by the fast moving traffic".
PC Barry Nicholas said: "It is a pretty horrific thing to do. There are plenty of places that re-home animals."
It is believed one kitten was black and white and the other a tortoiseshell.
Police are keen to hear from anyone who may have got a registration of the vehicle.
Anyone who may know the person responsible or has any information is asked to contact Falmouth Police on 101.