April 18 (UPI) -- Puerto Rico lost power across the island Wednesday -- a repeat of what happened last September when Hurricane Maria destroyed much of its power grid.
The island's power authority said it could take up to 36 hours to get electricity back -- with hospitals, Luis Muñoz Marín International Airport, the AAA pumping systems and banking center the top priorities.
Wednesday's power loss came less than a week after a tree fell during restoration work on a transmission system in Cayey -- and cut electricity for at least 900,000 people.
San Juan Mayor Carmen Yulin Cruz -- a heavy critic of post-Maria recovery efforts in Puerto Rico and U.S. President Donald Trump -- tweeted Wednesday the island's electrical system had gone "back to September 20."
"The entire electrical system in Puerto Rico collapses AGAIN!" she wrote.
Cruz said a Major League Baseball game between the Cleveland Indians and Minnesota Twins, however, would go on as planned Wednesday.
The mayor said emergency systems at Hiram Bithorn Stadium are "fully functional," and tower lights will be used for the game.
It wasn't immediately clear what caused the outage. Weather does not appear to be a factor, as winds were calm and skies were clear Wednesday.
Since Hurricane Maria, Puerto Rico has lost 3.4 billion customer hours of electricity -- making it the largest blackout in U.S. history, and the second largest power loss in world history.