Research in Motion (RIM) said Tuesday that recent upgrades it performed on its security infrastructure were to blame for the service outages that hit its BlackBerry devices this week.

RIM said in a statement that its initial investigation into the outages pointed to problems with the BlackBerry service infrastructure’s internal data routing system, which had been recently upgraded to increase overall capacity. While RIM says that such upgrades to its system are routine, it has found that this particular upgrade hit a snag that caused several service delays. RIM doesn’t specify why the system upgrade caused the outages, but the company notes that it fixed the problem quickly after identifying it, and that it expects no further complications with the upgrade.

RIM says that these findings are preliminary, that it is still investigating why the outages took place and that the company will “continue its in-depth diagnostic analysis and will share additional information as available.”

The disruptions first occurred Monday afternoon and affected customers of all major North American mobile operators and lasted for roughly two-and-a-half hours, interfering with their ability to send or receive messages, surf the Web or use the BlackBerry Internet Service Web site. While RIM has apologized to its customers for the inconvenience, the company also maintains that no messages were lost during any of the disruptions.

This week’s BlackBerry outage comes less than a year after a similar disruption knocked BlackBerry users offline last April. RIM said at the time that that particular outage was caused by the introduction of a software routine meant to optimize system cache memory.