Northwestel says it has found out what caused the communications failure in the Yukon two weeks ago.

Technicians blame the outage on a blown breaker that damaged some critical software.

Northwestel has asked Yukon Energy to audit the company's backup electrical system to guard against another outage.

Paul Flahety, the CEO of Northwestel, says they asked Yukon Energy to audit their backup system. (CBC)

"It was an unusual situation. Two forms of backup worked, but the fact they were cycling and we had this overload to the circuit, tripped this break and as I said the very next day we solved that and changed the wiring internally. But just to make sure there aren't any other possibilities, we are going through this audit with Yukon Energy's help to make sure there isn't a repeat," said Paul Flaherty, the CEO of Northwestel.

The communications outage crippled emergency services across the Yukon for most of the morning Sept. 20.

All telephones, cell phones and internet services were knocked out.

Yukoners say it's the first time in recent memory that all communication, including local telephones, was knocked out.

Northwestel says it is doing everything it can to ensure it does not happen again.