A bus driver was taken to hospital after a brick was thrown through the window of his vehicle.
Despite suffering a painful cut, he managed to keep control of the bus and bring it safely to a halt in Ennis Square, Dormanstown, Redcar, east Cleveland, on Sunday night.
Police are warning the culprits they will be caught and prosecuted.
Inspector Dave Mead said: "Throwing items at buses is extremely dangerous and similar incidents could lead to serious injuries and even death.
"We will not tolerate anyone throwing missiles at passing vehicles. You will be caught and you will be dealt with."
Iain McInroy, of Arriva North-East, said: "The safety of our employees is central to everything we do. This was an incredibly dangerous and irresponsible act and we urge anyone who has any information which could lead to the arrest of the culprits to contact the police."
In another incident, a youth is still being hunted after a hammer was thrown through a bus window, injuring a passenger.
The passenger suffered cuts and bruises and was badly shaken by his ordeal, which took place in Ingram Road, near its junction with Westerdale Road, Middlesbrough, at 7.50pm on Friday. The suspect, aged 13 or 14, is white.
Anyone who witnessed the Ennis Square incident is asked to call police on (01642) 304532. Anyone who sees people throwing missiles at vehicles is asked to call (01642) 326326.
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