A brilliant young mathematician studying at the University of Toronto went missing from his Edmonton home last weekend and those who know him don't believe he ran away.

Robert Barrington Leigh, 20, set out on his mountain bike from his family home around 10:30 p.m. Sunday, telling his parents he wanted to catch the tail end of a folk music festival near the city's river valley about a 10-minute ride away, his older brother Christopher said in a telephone interview.

Knowing he was unlikely to get into the festival so late, he said he would hang out to meet friends as they came out. About 11:30 p.m., he text-messaged his girlfriend to say he couldn't call her about a movie they planned that night, his brother said.

He hasn't been seen since.

Police and dozens of family members and friends who have searched the area since Tuesday haven't found a single clue to his whereabouts, Edmonton police spokesperson Lisa Lammi said.

That also means no evidence has been found to suggest anything untoward happened, Lammi said, noting detectives did step up their investigation, because records show Barrington Leigh has not used his cellphone or credit cards since he disappeared.

Police planned to stop searching the river valley at 6 p.m. yesterday, she said. Family and friends said they would continue searching.

The Barrington Leigh family home has been turned into a "Find Robert" headquarters, with multiple phone lines and a website featuring photos, a timeline of events leading to his disappearance and links to articles about the missing student's impressive achievements.

Friends or family who pick up the phone tell anyone who asks that Barrington Leigh is an introverted but happy young man with a tight circle of friends. Then they call him one of the brightest young minds in the country.

The whiz kid who won medals in international math and physics competitions could have graduated with two degrees — in math and physics — this spring after only three years at U of T, his brother said. Instead, he plans graduate work this fall.

"I don't understand the math he does and haven't for a long time," said Christopher, 12 years older, with a PhD in physics.

U of T has posted a link to the Barrington Leigh website. "He's part of our university community, so we are trying to do what we can from a distance," spokesperson Elaine Smith said.