Officials with AT&T Inc. and Verizon Wireless said BlackBerry maker Research in Motion Ltd. told them customers of all wireless carriers were affected.
It was not immediately clear how many of the 12 million worldwide BlackBerry subscribers had problems, as some users reported being able to access their service normally Monday afternoon.
But Garth Turner, a member of the Canadian Parliament, said during a caucus meeting that the incident - the second widespread disruption in 10 months - was having a big impact.
"Everyone's in crisis because they're all picking away at their BlackBerrys and nothing's happening," Turner said. "It's almost like cutting the phone cables or a total collapse in telegraph lines a century ago. It just isolates people in a way that's quite phenomenal."
Bell Canada spokesman Jason Laszlo said the majority of its BlackBerry customers were affected.
The BlackBerry service, which lets users check e-mail and access other data services on their handheld devices, has become a lifeline for many business executives and is increasingly popular among consumers with models like the BlackBerry Pearl.
In a statement, RIM said a "data service interruption" resulted in "intermittent service delays for BlackBerry subscribers in North America." The company said voice and text messaging services were not affected.
RIM later said data service was restored around 6:30 p.m. EST, about three hours after the outage began.
"No messages were lost and message queues began to be cleared after normal service levels were restored," the company said, apologizing to customers for the inconvenience.
There was no word on what caused the outage.
Major disruptions have been rare but often provoke an angry backlash against Waterloo, Ontario-based RIM because of its typically lengthy silences about the cause and because it eventually gives only cryptic, jargon-laden explanations.
When the BlackBerry service suffered a major outage last April, the company remained silent about the cause for two days.
The latest outage enraged some BlackBerry customers who were also hit by the network failure last year.
Stuart Gold, a customer who says he gets 1,000 e-mails a day as director of field marketing for Web analytics company Omniture Inc., worked on his laptop most of Monday after his BlackBerry went on the blink.
Although Gold said he thought last year's outage gave him a needed break from work, Monday's frayed his last nerve.
"I cannot believe this happened again," he said as he got off a plane. "I'm on the road 300 days a year. My entire life is in my BlackBerry - my family life, my professional life, my emotional life, everything. ... They're not allowed to do this to me."
Gold, 49, said he plans to ask his company to buy him a second smart phone from a rival as a backup. BlackBerry competitors include Palm Inc.'s Treo.
In a statement, AT&T spokesman Fletcher Cook said the company first learned about the problem from RIM about 3:30 p.m. EST.
"This is not an issue with AT&T's wireless network," Cook said.
RIM has deals with scores of wireless carriers to offer the BlackBerry service around the world.
AP Technology Writer Jordan Robertson in San Jose, Calif., and Associated Press Writer Rob Gillies in Toronto contributed to this report.