The FCC has warned that as many as 25 percent of cellphone towers in 10 states have been knocked out of service by Hurricane Sandy, along with a quarter of cable services.
There are far fewer problems with landlines, but the FCC says it expects more disruption as the storm progresses westwards.
"The storm is not over. And our assumption is that communications outages could get worse before they get better, particularly for mobile networks because of the flooding and loss of power," says FCC chairman Julius Genachowski.
The biggest problem is a lack of power, which has hit between seven and eight million people. While some cell sites are running on battery power, this could run out in the coming days. But flooding has also taken its toll, damaging other cell sites.
Calls to the few 911 call centers that have been lost are being rerouted, and the FCC's emergency response team has been working with FEMA and state and local officials to keep the service going.
But Genachowski is urging people to turn to text messaging and Facebook to keep in touch with their nearerst and dearest.
"We've seen broadband and social media continue to play an important role in communication for people during this storm," he says. "Social media is a critical platform for sharing information with loved ones. And it's been vital in keeping those other communications networks open for first responders."
Verizon says it's starting to restore service in areas where there's still power.
"Although we will be working with all available resources to restore service for our customers, some pockets of damage are extensive and could take up to a week or more to fully restore," says Bob Mudge, president of Verizon's Consumer and Mass Business division.
"Some restorals will require physical rebuilding of our facilities, and others will require the return of commercial power."
However, the company's experienced severe flooding at several key facilities in lower Manhattan, preventing it from providing back-up service.