A van driver was killed in a motorway crash after what "appears to be a lump of concrete" struck his windscreen and his vehicle hit a tree, police said.
Officers are treating the death of the man on the M11 near Birchanger, Essex, as suspicious.
The driver, in his 60s, died at the scene on Wednesday.
Essex Police were called to the northbound carriageway of the M11 between junctions seven and eight at 4.50pm and the carriageway was closed for investigations.
The Goose Lane bridge, which crosses the motorway, was also closed as part of the inquiry and officers want to speak to drivers who saw anyone acting suspiciously on the bridge.
They are also appealing for dash-cam footage taken in the area, between the junctions for Harlow and Bishop's Stortford, between 4pm and 6pm on Wednesday.