LUXEMBOURG, Dec. 23 (UPI) -- The Internet phone service Skype was back in business Thursday after an outage that lasted almost a day.
Skype, which is based in Luxembourg, was down most of Wednesday, USA Today reported. Service returned Thursday with video and audio calls being made at almost normal levels by noon EST.
The outage was the longest since 2007 and affected millions of users around the world. Some features remained unavailable or were running slowly Thursday afternoon.
Skype Chief Executive Officer Tony Bates, who has been on the job for only eight weeks, said the company apologizes to its members.
"The root cause was software," Bates told USA Today in a phone interview. "We had to temporarily bring in some dedicated servers and shift resources to get back online".
He said a malicious attack was unlikely.
Users in Japan, Europe and the United States all reported problems, which started Tuesday, the BBC reported. The company said the trouble has been traced to critical parts of its network being taken offline.
Bates said Skype lost about half of its estimated 20 million daily calls when the problem first occurred.
In a blog, the company said that the problem was caused by several "supernode" failures. Supernodes route traffic between users.
"Under normal circumstances, there are a large number of supernodes available," the blog read. "Unfortunately, today, many of them were taken offline by a problem affecting some versions of Skype".
The firm said its engineers were trying to create "mega-supernodes" to circumvent the problem. UPI
