Motorists are being told to seek an alternative route.
UPDATE FROM TVP -
The A5 between Portway junction and the A422 Stacey Bushes has now been reopened in both directions. Sorry for the inconvenience caused.
The North and Southbound carriageways on the A5 are currently closed between CMK Portway junction and A422 Stacey Bushes following a serious collision.
Thames Valley Police are telling drivers to ‘please seek an alternative route.’
MKFM will update this article as news comes in.