Three days of BlackBerry outages that spread to North America on Wednesday are being caused by a backlog of emails from Europe, the system's under-pressure owners said.

Facing anger from millions of customers starved of instant access to emails and messaging, Research In Motion (RIM) said it was working hard to fix the problem and insisted no messages would be lost.

RIM said an initial technical failure had prompted a build-up of messages in its network, triggering a cascade of problems around the world that affected many of the firm's 70 million subscribers.

"It is a backlog issue," RIM software vice president David Yach said, ruling out any rumors of sabotage or hacking.

"I know there is often speculation in these types of situation about a potential breach or a hack as the cause but we have seen no evidence to believe that this is the case," said Yach.

"Clearly we have a backlog in Europe," he said, "as you can imagine, with the global reach of BlackBerry and people using it to contact others around the world, there's a lot of messages to Europe from Asia and the Americas," he added.

"Over time that backlog has built up and affected our other systems."

RIM had earlier said "a core switch failure" and the breakdown of a backup switch had hit messaging, emails and Internet browsing in Europe, the Middle East and Africa on Monday.

Despite RIM's initial claim late Monday that the problem had been solved, the Canadian firm acknowledged Tuesday that some users in those areas, as well as in India, Brazil, Chile and Argentina, were experiencing messaging and browsing delays.

On Wednesday the firm confirmed the problems had spread to Canada and the United States.

The snowballing outages are the latest problem to beset the Canadian firm, which has faced weaker sales of the BlackBerry smartphone against rivals like Apple's iPhone, various models from HTC, and other handsets running Google's Android software.

In September merchant bank and activist shareholder Jaguar Financial began pressing for a shake-up in RIM's management, or a sale, merger or break-up of the company.

On Tuesday, Jaguar announced that it had the backing of eight percent of RIM shareholders for its proposal to split the company into three groups: a network company, a device company, and a patent company.

Shares in RIM, which have lost nearly 60 percent of their value this year, were down another 2.2 percent on the NASDAQ and 3.5 percent in Toronto at the close of markets Wednesday.

Market analysts said the hit this week was likely temporary.

"While this is a negative in the near term, particularly with high-profile smartphone launches coming from a major competitor, we view it only as a short-term disruption," said James Moorman of S&P Capital IQ.

"Despite competition from other smartphone launches, we continue to believe RIM will see solid smartphone volume in the near-term as carriers stock the new BB7 smartphones."