US software behemoth Microsoft has doubled a cash reward for information on the whereabouts of a Canadian boy who ran away from home after his father took away his Xbox game console, it said Tuesday.

Brandon Crisp, 15, took off on his bicycle from his Barrie, Ontario home on October 13 -- Canada's Thanksgiving holiday -- and rode east along an old rail line.

He has not been seen since.

His father told local media he had removed Brandon's Xbox, built by Microsoft, after noticing changes in behavior since Brandon started playing "Call of Duty 4: Modern Warfare" online.

The boy started skipping school, stealing money and ignoring his studies, his father said.

A local newspaper, the family's Internet service provider and Child Find offered a 25,000-dollar (19,500-dollar US) reward for information leading to his return.

Microsoft topped it up with another 25,000 dollars, the company said Tuesday in an email to AFP, "hoping for his swift return."

"Like everyone, we are deeply worried about the disappearance of Brandon Crisp," the company said.

Exhaustive searches have not turned up a single clue beyond the boy's bicycle, found last week with a flat tire.

Police are said to be examining who Brandon played with online. "Law enforcement has contacted Microsoft about this matter and we are cooperating fully with them," said Microsoft.

On Sunday, 1,600 volunteer searchers packed up their reflective vests and ended their efforts to find him, while police stopped their air and water search.

In an interview with the daily Globe and Mail, the boy's father, Steve Crisp, said he had not known how important the gaming system was to his son and how he would react when it was taken away

Experts commented that gamers may form bonds with fellow online players.

"This had become his identity, and I didn't realize how in-depth this was until I took his Xbox away," Steve Crisp told the Globe and Mail. "That's like cutting his legs off."

"This is such an issue that hits every parent out there, with video games that are starting to control our kids' lives," he said.

"I just took away his identity, so I can understand why he got so mad and took off. Before, I couldn't understand why he was taking off for taking his game away."

Now, Brandon's father says he just wants his son to come home.