A website that monitors network outages reports that on Monday night, many T-Mobile customers across the United States were unable to make or receive calls, send or receive texts, or access the internet.

Major cities including Chicago, Los Angeles, Las Vegas, Phoenix, New York, and Seattle are among those where the wireless provider reports operations are around normal levels but where service has been interrupted.

Consumers reported almost 83,000 issues at the height of the outage on Monday night at 10 p.m. Eastern time, according to DownDetector, an outage tracker that analyzes user-submitted data to generate service reports. T-Mobile did not reveal the total number of affected customers. Approximately 9,000 of them were left after midnight.

Users claiming to be from the following states have written comments on DownDetector: Arizona, California, Colorado, Florida, Hawaii, Kansas, Nebraska, North Carolina, Oklahoma, Texas, and Washington.

Twitter users whose service was disrupted said that their phones appeared to be in “SOS mode” and that they were unable to make standard calls but could make emergency calls.

T-Mobile tweeted that the service provider was working to resolve the disruptions, but provided no details on what was causing them or how long they would last.

VP of Technology at T-Mobile Neville Ray tweeted that the firm was working “rapidly” to resolve a “3rd party fiber interruption issue” that has been “intermittently disrupting certain voice, messaging, and data services in several regions.”

On Monday night, major wireless providers like Verizon Wireless and T-Mobile experienced brief service disruptions. Both Verizon and AT&T received over 1,200 and 2,000 event reports, respectively, at the height of the outages.

No one from T-Mobile, AT&T, or Verizon answered the phone right away.