Bell Canada said it was investigating the cause of Monday's two-hour BlackBerry service interruptions.

Customers of Bell Canada's BlackBerry wireless service experienced disruptions in the hand-held device's e-mail, video streaming and web browsing functions Monday afternoon, Bell said.

Beginning about 2 p.m. ET, Bell began receiving reports of BlackBerry service failures from users "from all over Canada," spokesperson Jason Laszlo told CBC News.

The problems, which affected customers linked to Bell's own wireless network and probably those roaming on a competitor network like SaskTel's in Saskatchewan, were resolved by 4 p.m., Laszlo said.

"We don't know the root cause. We're still investigating," Laszlo said. "It was intermittent, not a complete shutdown. For some people, it might have been sporadic."

Rogers Wireless, Canada's largest cellular provider, said it hadn't received any reports of problems with its BlackBerry service in Ontario or Quebec.

On June 22, all BlackBerry functionality was taken offline for four hours as the device's maker, Waterloo, Ont.-based Research in Motion Ltd., completed a planned upgrade to the servers that run the technology.

RIM had to deal with a major unscheduled outage in February, which took down 12 million customers for about three hours during the middle of the day.

Major disruptions have been rare but have often provoked an angry backlash against the company because of its typically lengthy silences about the cause and because it eventually gives only cryptic, jargon-laden explanations.

When BlackBerry service suffered a major outage in April 2007, the company remained silent about the cause for two days.