Walter Higgins, Chief Executive Office, Puerto Rico Electric Power Authority, center, speaks at the Senate Committee on Energy and Natural Resources on Capitol Hill in Washington, Tuesday, May 8, 2018. Sitting with Higgins are Christian Sobrino-Vega, left, Director at Government Development Bank for Puerto Rico and Jose H. Roman Morales, President of Puerto Rico's Energy Commission (PREC).(AP Photo/Pablo Martinez Monsivais)

SAN JUAN, Puerto Rico - Federal legislators grilled U.S. and Puerto Rico officials on Tuesday on why power has not been fully restored to the island nearly eight months after Hurricane Maria, and as a new storm season looms.

Lawmakers at a hearing of the U.S. Senate Committee on Energy & Natural Resources also questioned why the U.S. Army Corps of Engineers was pulling out of Puerto Rico next week.

"Tens of thousands of Americans there are still in the dark. The threat to their health and wellbeing is real," said Sen. Martin Heinrich, D-N.M. "If 20,000 Texans or Floridians were without power, I can't imagine FEMA saying 'Mission accomplished.'...It's reprehensible."

The concerns come as the Caribbean prepares for the start of hurricane season on June 1, and the new CEO of Puerto Rico's power company warned that restoring power to the more than 22,000 customers that remain in the dark has become increasingly difficult because of where they're located.

Several initiatives are underway to help strengthen the Electric Power Authority's system, said CEO Walter Higgins, but he noted that a grid nearly 80 per cent destroyed by the Category 4 storm had not been properly maintained for decades.

"I don't doubt we'll have some growing pains," he said. "It has not been maintained the way it needed to be. You just don't build a transmission tower and walk away and hope that everything will be fine."

The U.S. Army Corps of Engineers, which has been overseeing federal power restoration efforts, is leaving May 18 as determined by FEMA, and efforts to extend that deadline have not succeeded. So far, crews have repaired 69 per cent of sub-transmission lines and 88 per cent of transmission lines, said Charles Alexander Jr., the Corps' director of contingency operations and homeland security.

Carlos Monroig, a power company spokesman, told The Associated Press that the agency is in the process of contracting three new companies to replace crews once the Corps leaves.

As the next hurricane season approaches, the U.S. Department of Energy recommended that Puerto Rico immediately ensure that mutual aid agreements with power crews in the U.S. mainland are in place, said Bruce Walker, an assistant secretary with the department.

He also said crews are working to establish micro grids that would be able to keep providing power to a small region amid a broader blackout.

Higgins said the company is planning emergency drills ahead of any storms.

"We will have practiced and practiced and practiced to be as ready as possible for the next season," he said.

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Matthew Daly in Washington, D.C. contributed.

News from © The Associated Press, 2018