A widespread internet outage took down several websites including Amazon, UPS, and Southwest Airlines on Thursday.

The cause of the outage remains unknown, however, Akamai global content delivery network confirmed a widespread issue to its Edge DNS service. In a statement, Akamai said at 12:09 p.m. ET they are “aware of an emerging issue with the Edge DNS service.”

According to DownDetector, the outage is impacting PlayStation, Fidelity, FedEx, UPS, AirBNB, Home Depot, Disney, and more.

At 12:45 p.m. ET, most impacted websites were beginning to come back online.

In a statement on its website, Oracle acknowledged the Akamai issue is impacting its web services. 

Last month, a major outage hit Fastly and took down some of the world’s top websites. The company blamed the outage on a software bug that was triggered when a customer changed a setting.

The problem at Fastly meant internet users couldn’t connect to a host of popular websites including The New York Times, the Guardian, Twitch, Reddit and the British government’s homepage.

“We experienced a global outage due to an undiscovered software bug that surfaced on June 8 when it was triggered by a valid customer configuration change,” Nick Rockwell, Fastly’s senior vice president of engineering and infrastructure, said in a blog post.

He said the outage was “broad and severe” but the company quickly identified, isolated and disabled the problem and after 49 minutes, most of its network was up and running again. The bug had been included in a software update that was rolled out in May and Rockwell said the company is trying to figure out why it wasn’t detected during testing.

The incident highlighted how much of the global internet is dependent on a handful of behind-the-scenes companies like Fastly that provide vital infrastructure, and it amplified concerns about how vulnerable they are to more serious disruption.

The Associated Press contributed to this story.