BOISE, Idaho — The FCC said it will investigate CenturyLink over an outage Thursday that knocked out 911 in several locations and left customers across the country without internet service. As of midday Friday, CenturyLink said 911 calls were getting through.

"While our network is experiencing service disruptions, where CenturyLink is the 911 service provider 911 calls are completing," the company said in a tweet that went out at 2:43 p.m. ET Friday.

Service across much of the country was still out Friday afternoon, according to downdectector.com.

The company said Thursday night the problem involved a "network element" that was affecting services but didn't provide details. The outages stretched coast-to-coast and even temporarily shut down 911 emergency call services in some places.

Restoration has been slow going. As of late Thursday, the company tweeted that service would be fully restored within four hours.

But as the hours progressed, CenturyLink said it found new problems.

FCC Chairman Ajit Pai said he was calling on the Public Safety and Homeland Security Bureau to immediately launch an investigation.

"When an emergency strikes, it is critical that Americans are able to use 911 to reach those who can help. CenturyLink service outage is therefore completely unacceptable, and its breadth and duration are particularly troubling," Pai said.

The Associated Press contributed to this report.