Drivers are advised to find different routes and leave earlier this morning after incidents on the A421 in Bedfordshire and on the A1 in Cambridgeshire, near St Neots.
Both incidents are being dealt with by Bedfordshire Police and it is not known when the roads will be able to reopen.
Although the incidents are in two counties, the St Neots closure is just on the Bedfordshire/Cambridgeshire border and Bedfordshire drivers could be affected by both incidents.
The A421 is closed near Marston Moretaine following an incident just after 4am today and the A1 is closed between the B645/B1048 (St Neots) and A428 (Wyboston).
Diversions are in place for the A421 closure, from the M1 j13 drivers should take the A507 eastbound to Clophill, then proceeding on to the A6 northbound which re-joins A421 at Bedford.
For the A1 incident, on the A1 south, drivers should leave the A1 at (A14 J21) Brampton Hut, take A14 east and proceed to J24 (Godmanchester). At J24 they should then use A1198 south to Papworth to join B1040, then follow B1040 to A428 and take A428 (W) to A1.
Drivers travelling northbound should take the reverse route.
Duty operations manager for Highways England in the East, Ray George, said: “We are working closely with police to reopen these roads as soon as possible, but it is difficult to say how long that will be at this stage as accident investigation needs to take place. We would advise drivers to find alternative routes if at all possible.”
More updates are available at @HighwaysEAST