Police were hunting for a pair of teenage boys today after two concrete slabs were thrown from a bridge on to a lorry in what officers branded a "reckless act".
The slabs were thrown from the bridge over the A10 in Cheshunt, Hertfordshire, at about 5.15pm last Thursday, a police spokeswoman said.
It is believed two teenage boys, who were standing on the Cheshunt footbridge over the northbound carriageway, waved at the driver of a white Daf lorry.
As the trucker passed under footbridge, he heard two loud bangs.
When he inspected his vehicle, he found two slabs of concrete paving had gone through the fibreglass roof and landed inside.
The two boys were described as white and aged between 11 and 16.
Police Constable Nicholas Shuttlewood, from Hertfordshire Police, said: "This reckless act has not only caused around £1,700 damage to the lorry, but has put the driver's life and other road users' lives in serious danger.
"I am extremely keen to speak to anyone who believes they saw these two boys on the bridge and can help us identify them.
"If you can help, please call me via the non-emergency number on 0845 33 00 222. Alternatively, you can call Crimestoppers, the independent charity, anonymously on 0800 555 111."Reuse content