(Rewrites, adds details of situation in Puerto Rico)
SAN JUAN, Puerto Rico/NEW YORK, Sept 26 (Reuters) - Broken electricity poles and streetlights list into the middle of highways. Satellite images show an island devoid of light. Cellular phone service is non-existent.
Hurricane Maria's devastation of the U.S. territory of Puerto Rico last week left the entire island and its 3.4 million residents without power.
Officials are still only assessing what is needed to kick off a months-long effort to bring back electricity, meaning millions of people could face an extended period without access to clean water, refrigeration, safe food and medical supplies.
Maria struck Puerto Rico as a very dangerous Category 4 hurricane on Wednesday, with winds up to 155 miles per hour (249 km per hour), leveling large swathes of the island, killing at least 10 residents and cutting off power and telecommunications services.
Highway signs and traffic poles were scattered across highways around the island on Monday, with intersections turned into obstacle courses as cars drove over and around tangled wires and other debris.
Unlike Hurricane Irma a week earlier, where tens of thousands of utility workers streamed into Florida shortly after that storm swept through the state, those dedicated to assessing the damage to Puerto Rico's degraded electrical grid were only starting to get the full measure of the destruction.
A full damage assessment has been difficult because of the limited ability to get flights to the island and as federal agencies have been concentrating on life-saving efforts and providing power to crucial infrastructure like hospitals.
Rebuilding will be a challenging task for the island's bankrupt electric utility, Puerto Rico Electric Power Authority (PREPA), already regularly criticized by residents for frequent outages and rates higher than every U.S. state other than Hawaii.
Preliminary assessments suggest about 55 percent of the island's transmission towers have been destroyed, according to industry group the American Public Power Association, which is working with the U.S. Federal Emergency Management Agency on relief efforts.
About 90 percent of the distribution network, which brings power to residents and businesses, is out of commission, APPA said. Nighttime satellite images released by the U.S. National Oceanic and Atmospheric Administration show the island early on Monday almost entirely without light.
The U.S. Federal Communications Commission said Monday that 91 percent of cellular sites in Puerto Rico remain out of service. Outside San Juan, the capital, cell service was virtually non-existent, and residents said they have been unable to communicate with relatives and friends, be they distant or merely just in another part of the island.
In Florida following Irma, a Reuters witness saw convoys of utility vehicles around the state, but in Puerto Rico, signs of activity were sparse, with just the occasional utility crew seen.
APPA on Monday said that assessment needed to be finished before it could get public power utilities to send crews and equipment. The New York Power Authority had sent a crew of a dozen on Friday, with drones.
"There are many logistics to coordinate," said Mike Hyland, APPA senior vice president in engineering services. "We need to know where the crews will be housed and if we can ensure their safety and health so they can be effective."
The reconstruction looks to be arduous, Hyland said. Broken transmission towers - heavy steel structures up to 150 feet (46 meters) tall that support high-voltage wires - were visible around Puerto Rico. They may need to be airlifted off the island, rebuilt, and then transported back, he said.
The rates PREPA charges weren't enough for the utility to maintain its infrastructure, in part due to ineffective collection efforts, and long-standing mismanagement had left it in a $9-billion hole before declaring bankruptcy in July this year.
"The country is likely going to be without power for months," said Ismael Perez, an engineer and resident. The national utility needs to be depoliticized or privatized, he said.
PREPA's equipment was already "degraded and unsafe," according to a draft fiscal report the utility filed in April. A source familiar with the bankruptcy said he has been told that power generation assets "came through in reasonably good shape," while the power lines did not.
Unlike the continental United States, where one utility can draw on another's power during emergencies, PREPA is the only provider in Puerto Rico.
"It's not an easy thing to restore power to an island," said Najmedin Meshkati, an engineering professor at the University of Southern California specializing in disaster recovery.
"There is no neighboring utility that can help transmit power or easily send crews over to help." (Reporting by Robin Respaut in San Juan and Scott DiSavino in New York; Additional reporting by Dave Graham in San Juan and Stephanie Kelly in New York; Writing by David Gaffen; Editing by Joseph Radford and Bill Rigby)