Police are looking for a man and a woman who might be lost on or around the mountain.
They say it is believed that a couple departed the tram from Laxey at lunchtime to the summit.
They have then set off walking in the direction of Laxey shortly after.
The man is white, of stocky build, late 30s/early 40s with grey hair.
The woman is white with ginger/brown hair wearing an orange/red jacket.