VANDALS caused "mayhem" on the M4 motorway through Newport yesterday after they switched on lane closure signs at the Brynglas Tunnels.

Police believe that youths flicked the switch which illuminated big a big red cross, indicating that the lane is closed, above the outside lane of the westbound carriageway through the busy tunnel.

A Gwent Police spokesman said: "The signs in the Brynglas Tunnels are controlled locally.

"And it appears the vandals found the control box and switched on the lane closure sign, which is a big red cross, above the outside lane of the westbound carriageway in the tunnel.

"It caused mayhem as cars were slowing down to change lanes because they thought there was an obstruction in front - but there was not.

"It caused congestion but luckily no accidents." Police have warned that if anyone is caught interfering with motorway information signs they face "serious punishment".

The incident happened at about 5pm yesterday. Traffic Police have surveyed CCTV camera footage near the tunnels which shows a group of youths in the area at the time.

Anyone with any information is urged to call Gwent Police traffic department on 01633 838111.