About 25 percent of the cell sites in the 10-state area were out of service at 10 a.m. Eastern on Tuesday, the U.S. Federal Communications Commission estimated. Due to the floods, high winds and snow brought by the storm, there were reports of outages as far west as Michigan, the agency said. The situation could become worse in some areas as backup power supplies for affected cell sites run out, it warned.

A small number of 911 call centers went out of service, and calls to them were redirected to other 911 facilities, an FCC representative said on Tuesday. Some of those redirected calls came across without location information, and the FCC is investigating that problem, the representative said.

Service providers were still evaluating the effects of the wide-ranging storm late Tuesday. Verizon Communications said more than 200 of its wireline facilities were running on backup 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," Bob Mudge, president of Verizon's Consumer and Mass Business division, said in a press release.

Verizon Wireless said 94 percent of its cell sites in the Northeast were up and running and all its switching and data centers were functioning normally. But extensive flooding in the hardest-hit areas, including Lower Manhattan and parts of New Jersey, caused problems for both wireline and wireless carriers. Power outages also affected service, and in some cases carriers were waiting for electric utility crews to finish their work.

"The storm surge from Hurricane Sandy has resulted in flooding at several Verizon Central Offices in Lower Manhattan, Queens, and Long Island causing power failures and rendering back-up power systems at these sites inoperable," Verizon Communications said in the release. "While these sites are currently on battery power, the inevitable loss of power requires that all equipment at these sites be powered down to prevent damage." Customers served by those central offices lost all FiOS, DSL (digital subscriber line) and wireline voice service, Verizon said.