Vehicles hit by items thrown on to A14 in Suffolk
Four vehicles including an ambulance have been damaged on the A14 in Suffolk by objects thrown on to the carriageway from a country lane.
Calls to police at 16:20 GMT claimed stones and concrete rubble had been thrown at vehicles at Trimley St Mary.
Two lorries had a window and cab damaged, while the windscreen of an ambulance was cracked and a car's side window was damaged.
Officers are searching the A14 with the help of the police helicopter.
Sgt Julian Ditcham, from Suffolk Police, said up to five youths had been seen throwing items from the side of the road near the Trimley overbridge.
He said: "It started with mud but also stones and concrete pieces up to about 6in (15cm) wide were thrown. The youths were near a country lane accessed from a nearby estate.
"The incident could have far worse resulting in life-threatening if not fatal injuries. I urge drivers to be vigilant."
He said the incident had similarities with ones earlier this month in Essex.
On 1 December, car passenger Carol Manley was seriously injured when a concrete bollard fell from a bridge onto her car on the A12 near Galleywood in Essex.
Forty minutes earlier, a large lump of granite smashed a car windscreen but did not harm mother and daughter Stella and Lisa Horne, who were on the A12 at Ingatestone.
Essex Police are treating those two incidents as attempted murder.