The accident near J17 for Rugby in Warwickshire is causing rush hour travel chaos.
Traffic is queuing for more than three miles with delays of at least 30 minutes.
Highways England wrote online: “This closure is due to a serious road traffic collision involving a number of HGVs”.
They tweeted that the closure is expected to continue into “morning peak” and that motorists should “consider your route if heading for London and the south east.”
The crash is thought to have taken place near J17 with traffic backed up to J18.
Motorists have been advised to try and avoid the area.
Traffic conditions are expected to return to normal by midday today.
The M45 eastbound to the M1 is also closed at the B4429 junction at Dunchurch.
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