Motorists are being advised to avoid the Mount Rule Road area after a crash earlier.
Traffic is said to be heavy after the incident, which happened shortly after 1.30pm.
Officers say the crossing point onto Eyreton Road is shut.
Emergency service vehicles are also using the TT access road, which is said to be causing delays there.
Woman releases fundraising poetry book
Castletown hosts tin bath racing
Mountain Road closed for skateboarding today
Peel ready for huge community sale later
Cruise ship makes first stop of week
Tin bath races mean bus diversions tomorrow
MHK wants backing for changes to Tynwald members' pay
Storage firm announces closure