NEW YORK -- AT&T is reimbursing customers for the nearly 12-hour network outage on Thursday, the company announced in a news release.

The mobile network will issue a US$5 credit to 鈥減otentially impacted鈥 AT&T Wireless customers, which it says is the 鈥渁verage cost of a full day of service.鈥

鈥淲e recognize the frustration this outage has caused and know we let many of our customers down,鈥 the company said late Saturday. 鈥淲e understand this may have impacted their ability to connect with family, friends, and others. Small business owners may have been impacted, potentially disrupting an essential way they connect with customers.鈥

The credit will not apply to customers under AT&T鈥檚 Business or Prepaid plans or those who have Cricket Wireless accounts. AT&T acquired Cricket in 2014 for about US$1.2 billion.

The network outage, which was first reported on Thursday at 3:30 a.m. ET, prevented tens of thousands of subscribers across the United States from fully accessing calls, texts, internet and emergency services. AT&T had encountered sporadic service interruptions in the days leading up to the outage, including a temporary 911 outage in some parts of the southeast.

While regional disruptions to wireless service happen occasionally, prolonged nationwide outages are rare. The Federal Communications Commission confirmed Thursday it was investigating the incident.

The US Cybersecurity and Infrastructure Security Agency also told CNN on Thursday it was 鈥渨orking closely with AT&T to understand the cause of the outage and its impacts, and stand ready to offer any assistance needed.鈥

Several hours after service was restored, AT&T released an update stating the outage seemed to be the result of an internal issue, not a cybersecurity threat.

鈥淏ased on our initial review, we believe that today鈥檚 outage was caused by the application and execution of an incorrect process used as we were expanding our network,鈥 the company said.

On Saturday, AT&T reiterated it was taking steps 鈥渢o prevent this from happening again in the future,鈥 but did not elaborate.