A van is currently on fire on the M1 at Junction 29a.
Highways England said the van is on the northbound carriageway.
Lanes one and two have been closed to traffic on the M1 and the entry slip at J29A northbound is also closed.
A highways spokesman said: "There is heavy smoke in the area."
Update at 3,40pm
Highways England said: "All lanes on the M1 northbound past J29a Markham Vale. The slip road has now fully reopened."