Police are investigating a motorcycle crash near Mayfield yesterday afternoon where a Mowbray man was seriously injured.

Around 4.30pm a male motorbike rider crashed his motorbike on a Crown Land trail around 400metres off-road from Hargrave Crescent near Mayfield.

The 35-year-old man was riding an unregistered Thumpster trail bike in a southerly direction on the trail when he lost control of the bike, travelled down an embankment and collided with a tree.

The rider was unlicensed and it is believed drugs and or alcohol may be contributing factors to the crash.

The man was transported to the Launceston General Hospital with serious injuries.

Late last night the man was transferred to the Royal Hobart Hospital in a critical condition.

Police would like to speak to anyone who saw the rider or bike prior to, or around the time of the crash. Information can be provided to Tasmania Police on 131 444 or Crime Stoppers anonymously on 1800 333 000.