(CNN) 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.

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