Milton Keynes commuters are being warned of a serious crash on the M1 which has caused all lanes to be closed.
And drivers are being urged to avoid the area as it will have a knock-on effect.
All lanes south and northbound between junctions 15a for Northampton to 16 for Daventry are shut following the incident at around 2pm.
Northamptonshire Police tweeted: "Officers are currently at the scene of a serious road traffic collision on the M1, between junction 15a and junction 16.
"The motorway has been closed in both directions. Please seek an alternative route until further notice."
The M1 southbound may not reopen until 5.30pm, Northamptonshire Highways has tweeted - a diversion is in place.