Nearly half a million customers remain without power in Puerto Rico more than four months after Hurricane Maria battered the US territory, according to the island’s electric power authority.

Still, the beleaguered Puerto Rico Electric Power Authority, or PREPA, announced what it called a “major milestone” in the recovery from the September storm, with the restoration of power to more than 1 million clients Wednesday.

“We still have several hundred thousand residents and business owners who remain without power, which is unacceptable,” Justo Gonzalez, PREPA’s interim executive director, said in a statement.

More than 450,000 customers remain in the dark, the utility said.

A government website said Thursday that 68.25% of the utility’s customers have power.

The utility has said customers include residential, commercial and industrial clients. It’s unclear how many individual people continue to struggle through Maria’s aftermath in darkness.

Puerto Rico’s 3.4 million citizens have endured months of hardship since Maria made landfall on September 20 with 155 mph winds.

Thousands still await government-issued tarps as temporary replacements to roofs blown away by the storm. More than 170 displaced residents remain in nine shelters across the island, while nearly 900 others have been temporarily put up in hotels by the Federal Emergency Management Agency.

The PREPA statement said it is working with state and federal agencies, including the US Army Corps of Engineers and FEMA, as well as power industry contractors “to execute an aggressive plan to advance the restoration.”

PREPA came under fire late last year after entering into a controversial $300 million contract with Whitefish Energy, a small Montana-based firm that employed two people when the storm hit.

Hurricane Maria was a Category 4 hurricane when it struck Puerto Rico. It was the strongest storm to hit the island in 85 years and left much of it without power or water.