The statewide 911 outage on Tuesday was caused by a firewall security system built into the emergency notification network, according to a preliminary finding by the state.

The Massachusetts 911 Department and the service’s managing contractor, Comtech, determined that a firewall prevented calls from going through the system for two hours on Tuesday, from approximately 1:15-3:15 p.m., according to an update  from the department.

“Comtech’s initial review of the incident has confirmed that the interruption was not the result of a cyberattack or hack,” the department said in a statement.

Exactly why the system’s firewall security blocked calls, however, remains under investigation.

The 911 Department said it was not aware of any emergencies that went unattended as a result of the outage.

“Although some calls may not have gone through, the system allows dispatch centers to identify the phone number of callers and return those calls. The Department has not received any reports of emergencies impacted during the interruption,” the department said in the update.

“The Massachusetts State 911 Department is deeply committed to providing reliable, state-of-the-art 911 services to all Massachusetts residents and visitors in an emergency. The Department will take all necessary steps to prevent a future occurrence,” said Executive Director of the State 911 Department Frank Pozniak. “We are grateful to everyone for their patience and cooperation during the outage.”

– Developing