The Amber Alert has been lifted but police are still searching for a missing autistic Hamilton-area teen believed to be with his father.

Austin Large, 13, and his father Elias Large were to have left Friday for a fishing trip in the Lake Nipissing area, but Austin wasn't returned to his mother on Monday as scheduled.

Suspicions were further raised when it was learned the two didn't even go to Lake Nipissing and that it was rare for the boy to go with his father, who is estranged from Austin's mother. She has full custody of Austin.

The teen only has enough medication to last until today.

Police issued the Amber Alert on Monday, but cancelled it late that night.

Tips as to their whereabouts have been few.

"We had a credible call ... Saturday afternoon. He was seen and well and travelling towards Manitoulin Island," Det.-Sgt. Chris Kiriakopoulos of Hamilton Police told CTV Toronto.

However, no further leads have surfaced, he said.

The two are believed to be travelling in a 1999 GMC Sierra truck-extended, with a white, large green tool box with Ontario licence plate number NE7 917.

Austin is described as 5 foot five inches, 160 pounds. He has brush-cut light brown hair, blue eyes and a heavy build.

With a report from CTV Toronto's Jim Junkin