The body of a 13-year-old snowmobiler was found Monday afternoon, after a father and son from Ile Bizard went missing on a snowmobile trip around supper time Sunday.

Police are still looking for the boy's father, but the search has been called off for the night due to darkness. It will resume at 8:30 a.m. Tuesday.

Divers began searching the Lake of Two Mountains Monday morning, with help of a helicopter.

Polie say they found the snowmobile first, then the body.

"Fifty feet from the Ski-Doo, the dive team found one body, which will be examined by the coroner," said Christopher Harding from the Deux-Montagnes regional police force.

An eyewitness told police he saw their vehicle fall through the ice, around the same time the 38-year-old and his 13-year-old son vanished.  

Police say they are unsure exactly what happened, but inexperience, riding at night and riding off-trail were likely all factors.

"This was at night, so did the people lose their bearings? They they get lost?... These are all possibilities we'll have to look into," said Harding.

The trail the snowmobilers were using was not officially marked. Police are repeating the advice they give every year -- don't drive snowmobiles on unmarked trails.