Reports say the A421 is blocked between the Whaddon and Newton Longville junctions.
There are currently delays on the A421 in both directions.
Traffic issues were first reported at around 11.45am today.
AA Traffic news said: "Severe delays of 15 minutes and delays increasing on Bottledump Roundabout Westbound between A421 Standing Way and A421. Average speed five mph."
There is currently no other information.
MKFM will keep this article updated.