People congregate in front of a building that still has wireless internet access in the aftermath of Hurricane Sandy in New York Oct. 30. (BRENDAN MCDERMID/REUTERS)

Four days after disaster struck the Eastern seaboard, scores of New York and New Jersey residents complain they still aren’t able to make cell phone calls or use the Internet.

As of Thursday afternoon, areas affected by Hurricane Sandy were slowly seeing cellular phone, Internet and television service restored, according to the FCC.

The proportion of inoperable cell sites declined to 19 percent from 25 percent in those areas, the FCC said, according to Thursday morning data.

But the blackout in communications has been frustratingly drawn out. And as of Thursday, progress in restoring the world’s most advanced communications technology was challenged by a remarkably rudimentary problem: gas.

There just wasn’t enough fuel for Verizon and other companies to keep backup generators going to power cell towers and switching facilities, companies said.

“The availability of fuel to keep generators delivering backup power to switching facilities and other critical network equipment is an increasing challenge in hard-hit areas such as New Jersey and New York,” Verizon said in a statement Thursday afternoon.

Also problematic was downed trees and flooding that kept crews from repairing cell towers, companies said.

“Our commercial communications networks are essential to emergency response and recovery efforts, as well as to commercial activities and connecting with family,” FCC Chairman Julius Genachowski said in a statement late Thursday.

Time and again, the limitations of cellular and Internet technology are revealed during natural disaster. Traditional copper-wire phones, known as plain old telephones or POTS, are built more reliably than cellular service, some analysts say.

“Copper-wire phone networks were built with stability and dependability in mind because they were public utilities and were supposed to withstand hurricanes and floods,” said Harold Feld, a senior vice president at public interest group Public Knowledge.

Increasingly, Americans have abandoned their wireline phones for wireless service.

Nearly 40 percent of American homes have cut wireline phone service for wireless-only. Only about 10 percent of Americans have just landline service, according to communications service trade group US Telecom.