South Dakota experienced a statewide outage at about 5 p.m. EDT during which it said texting 911 was still an option and returned to power about two hours later. Las Vegas Metropolitan Police, the largest law enforcement office in Nevada, post service at about 4 p.m. EDT. Locals were asked to make calls to them using their mobile devices, which law enforcement were able to see and call back but said that calls from landlines did not work during the outage.

In Del Rio, Texas, police communications supervisor Juan Hernandez said people using T-Mobile could not contact them. The opposite was true in Nebraska, where most cell phones could not contact 911 except for T-Mobile customers. All customers returned to service at about 4 a.m. on Thursday.

The National Emergency Number Association said trained public safety dispatchers handle about 240 million calls annually in the United States.

The cause of the outage was not immediately known but Mark Molzen a spokesperson for the telecommunications company Lumen Technologies told NBC News it had experienced an outage.

“On April 17, some customers in Nevada, South Dakota and Nebraska experienced an outage due to a third-party company installing a light pole — unrelated to our services,” Molzen said. “We restored all services in approximately tow and a half hours.”

An AT&T outage across the United States in February hampered 911 facilities in California, North Carolina and Texas. In 2023, problems with the 911 system in suburban Washington, D.C. prevented residents from making calls to emergency lines in Arlington and Alexandria, Va.

AT&T on Thursday told NBC News that its network was “operating normally” and that the outage was not related to an issue with FirstNet its nationwide broadband for public safety.

“There appeared to be an issue on another carrier’s network that could have affected 911 calls,” an AT&T spokesperson said.