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A transmission line failure Thursday left thousands in Puerto Rico without power, just after areas had finally seen a restoration of electricity following Puerto Rico's blackout after Hurricane Maria.

The Puerto Rico Electric Power Authority confirmed that as of Thursday afternoon, the island was only at 18 percent power generation compared to 43.2 percent in the early morning.

The failure in the 230-kilovolt transmission line that runs from Arecibo to Manatí caused the loss of power mainly in the San Juan metropolitan area, including the municipalities of Manatí, Bayamón, Caguas, Guaynabo and Carolina.

A worker of Puerto Rico's Electric Power Authority (PREPA) repairs part of the electrical grid after Hurricane Maria hit the area in September, in Manati, Puerto Rico October 30, 2017. REUTERS/Alvin Baez ALVIN BAEZ / Reuters

The failure took place in the same transmission line that had been repaired previously by Whitefish Energy, a Montana firm recently under scrutiny for a $300 million contract to restore power on the island. The deal was later canceled by the Puerto Rico government after being publicly criticized by officials.

The current outage is not tied to the previous work, said Whitefish spokesperson Chris Chiames. "None of the issues reported today with the outage have anything to do with the repairs Whitefish Energy performed."

Authorities say they are expecting that service may be restored starting tonight in some of the affected areas; it could take about 12 to 18 hours.

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