Many users around the world could not access the YouTube site for about two hours on Sunday.
The company blamed the outage on erroneous routing information introduced by a Pakistani ISP after Pakistani authorities ordered ISPs there to block the site on Friday.
Traffic to YouTube was misrouted for around two hours, rendering the site inaccessible for many users around the world, YouTube said on Monday.
"We have determined that the source of these events was a network in Pakistan," the company said, adding that it is still investigating the problem to prevent it from happening again.
The Pakistan Telecommunication Authority (PTA) ordered the country's ISPs to block users access to YouTube on Friday because of an inflammatory anti-Islamic video on the site, Wahaj us Siraj, convener of the Association of Pakistan Internet Service Providers said in a telephone interview on Monday.
If the video is provocative, then it is better it is removed, rather than provoke unrest in Pakistan, said Siraj who added that he did not know the contents of the video.
Access to YouTube is still blocked in Pakistan while the ISPs work with the PTA to narrow its order to block a single URL (Uniform Resource Locator) pointing to the video, Siraj said. He expects the PTA to make an order to that effect later on Monday.
Steven Schwankert in Beijing contributed to this report.