(Adds comment from LUMA on mayors' concerns)
By Ivelisse Rivera
SAN JUAN, Sept 26 (Reuters) - Puerto Rican government workers tried to restore power on Monday amid growing frustration over the slow response from the main energy provider, with about 40% of the island still without electricity more than a week after Hurricane Fiona hit services.
As of 1 p.m. (1700 GMT) on Monday, Puerto Rico grid operator LUMA Energy said power had been restored to 59% of its roughly 1.5 million customers following the Sept. 18 arrival of Fiona, at the time a Category 1 hurricane that caused almost all the island's roughly 3.3 million residents to lose power.
Local officials sent city workers to patch up the systems themselves on Monday.
"We are going to take to the streets this afternoon since LUMA is not answering," said Luis Javier Hernandez, mayor of Villalba, a municipality in central Puerto Rico.
Teams of municipal workers planned to raise fallen poles, collect downed cables and speed restoration of electricity, Hernandez said, adding his town is completely without power.
Hernandez said LUMA had failed to communicate clearly about how it would help Villalba regain service.
Members of a mayors association told a news conference in Isabela, a region on the northwest coast, that other municipalities would send out crews to raise polls and lines.
Melissa Pueyo, a LUMA director, said her company was working to restore power as quickly and safely as possible.
She pointed to hurdles such as storm-damaged roads and factors beyond LUMA's control, such as the generation capacity of the Puerto Rico Electric Power Authority (PREPA).
"We definitely understand the frustrations that mayors have," Pueyo said.
"We continue to let them know that we are working as fast as we can," she said.
Pueyo welcomed help from municipal workers in moving fallen poles and debris but said those crews should not be working directly on power lines or breakers.
PowerOutage.us, which estimates outages based on utility data, said about 600,000 of a total of 1.468 million customers remained without service on Monday afternoon, based on information from LUMA.
LUMA expects 91% of the island will have power by Friday.
The widespread outages have led to a cascade of energy problems for Puerto Rico. Fuel distribution limitations and surging demand for fuel to run backup generators have left many gas stations dry.
Fiona turned into a post-tropical cyclone by the U.S. National Hurricane Center on Saturday, battered Puerto Rico and other parts of the Caribbean a week ago. Health officials in Puerto Rico attributed 12 deaths to the storm in Puerto Rico. people.
The storm has brought back painful memories for many Puerto Ricans of the devastation caused by Hurricane Maria five years ago, which killed thousands of people and knocked out power to nearly all customers for weeks.
When Maria hit the island as a powerful Category 5 storm, PREPA owned and operated the power grid.
Last year, LUMA, a joint venture by units of Canadian energy firm ATCO Ltd and U.S. energy contractor Quanta Services Inc, took over operations. PREPA still owns much of the infrastructure.
"This is a very old and dilapidated system," said LUMA spokesman Hugo Sorrentini. "It's suffered years if not decades of neglect."
Hundreds marched in Puerto Rico's capital of San Juan in July to demand the government cancel its contract with LUMA over chronic power outages and frequent rate hikes.
Despite roughly $12.5 billion in federal funds being approved for spending to modernize Puerto Rico's grid after Maria, academics and analysts say bureaucratic holdups, policy disagreements and other dilemmas have stalled the spending process.
(Reporting by Ivelisse Rivera in San Juan, Puerto Rico. Writing by Laila Kearney in New York; Additional reporting by Donna Bryson; Editing by Josie Kao and Sam Holmes)