The incident, which is believed to involve one vehicle, happened on Douglas Road near Ballasalla.
Police have asked the public to avoid the area while they deal with the incident.
In an online update issued at 8.41am, officers said southbound traffic could filter through the scene towards Ballasalla.
Drivers travelling southbound are being diverted via Orrisdale Road.
Those heading north are being diverted at Whitestone towards St Marks.
Heavy traffic remains in the area and delays are expected.
It is understood temporary traffic lights linked to roadworks in St Marks are adding to congestion around the scene.
A number of motorists have contacted Isle of Man Today to report long traffic queues around the scene.
The Isle of Man Constabulary said: ‘The whole area is blocked due to the volume of traffic.’