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DES MOINES, Iowa — A large number of Iowans could not get online Tuesday afternoon due to a widespread Internet outage. Mediacom, the internet provider whose service went down, now believes it knows the cause of the outage.

In a statement, a Mediacom spokesperson said the outage was caused by a software bug to a large router operated by a third-party, which left the situation “beyond Mediacom’s control.” The situation left 40 percent of its Iowa service area without internet at about 3 p.m. on Tuesday.

The company said it has installed software updates and rebooted its system since the outage.

A full statement from company spokesperson Phyllis Peters is available below:

All of us at Mediacom regret that our broadband customers in about 40 percent of our Iowa service area experienced a service disruption on Tuesday afternoon.  The incident occurred at a few minutes before 3 pm CST on Tuesday and lasted for an hour.  For some of the same customers, the service outage re-occurred between 6 pm and 7 pm (there was no impact on video / TV service).

The outage was caused by a previously unknown bug in the software running on a large Cisco aggregation router, something that was beyond Mediacom’s control.  Mediacom and Cisco engineers performed several reboots and software updates, and also added replacement equipment in order to restore services to affected customers.  This was not an electronics failure, although that was a suspected cause at the early outset of the issue.  A software bug adversely affected the routing of data signals (internet traffic).

We recognize how vitally important it is to maintain connections 24/7, and we apologize for the frustration and disruption this caused customers.  Our network engineers provide 24/7 monitoring of all aspects of our network, and fortunately, we also have the ability to immediately add the expertise of technology developers and partners. The immediate collaboration with our Mediacom team on Tuesday helped to reduce the time of this interruption.  It’s human nature to remember the “down times” and not think about the 99.99% of the time when there are no network interruptions.  We’re proud of Mediacom’s high network reliability ratings and the integrity of a network that powers more Gigabit-speed broadband users in Iowa than any other provider.