The truck overturned on the slip road leading from the M11 to the clockwise M25 at Theydon Garnon, near Epping, Essex, shortly before 12:00 GMT.
It led to the closure of the exit slip road to the northbound M11.
A Highways Agency spokesman said an "extensive specialist clean-up" was under way on the M11 but warned drivers to expect severe delays.
A lorry has shed dozens of bags of lard on to a busy motorway intersection, leading to severe delays.