NEW YORK — Wireless networks fell quiet Sunday in some coastal areas of North Carolina and southern Virginia, but calls were going through in most areas affected by Tropical Storm Irene, the Federal Communications Commission said.

In Lenoir, Greene and Carteret counties of North Carolina, 50 percent to 90 percent of cell towers went offline, said Rear Adm. Jamie Barnett, head of the public safety bureau of the Federal Communications Commission.

About 400 cell towers were offline in North Carolina and Virginia, with power outages the chief reason. Another 200 were running on backup power by Saturday and could go silent as their backup batteries or generators run dry, Barnett said.

Landline phone service failed for about 125,000 households on the coast, the FCC said. Another 250,000 have lost cable service, and some of them could have phone service from the cable company, which would then also be out.

FCC Chairman Julius Genachowski said the 911 system has held up well. There were no reports of call-center outages or call congestion, he told The Associated Press.

Public-safety networks for police, firefighters and ambulance crews also were working.