A lorry which overturned hitting a bridge and a central reservation has been recovered, National Highways said.
Essex Police said the crash happened on the southbound carriageway near Witham at about 02:40 GMT.
The road was shut between junctions 22 for Rivenhall and 21 for Witham, with diversions in place via the A120, A131 and A130.
The lorry driver was arrested on suspicion of failing to provide a specimen for testing.
National Highways said a barrier had been damaged in the crash but the road had reopened.