Police say they are concerned about an increase in reports of “mindless” vandals firing missiles through windows in Leeds.
Officers were called after marbles were shot into a house in Pudsey last week.
It comes several months after a spate of similar incidents in the same area.
A spokesman for the Leeds Outwer West Neighbourhood Policing Team said: “It seemed to go away but we are now getting increased reports again. The working theory is they are using high-velocity catapults to fire these at windows.
“This seems to be some sort of entertainment to them but we need to put a stop to this mindless activity. They could be as dangerous as a bullet.”
Most of the reports have been between 10pm and 11pm.
Police say they will talk to schools about the issue and have appealed for information.