The vast majority of Puerto Rican homes have been plunged into darkness after Hurricane Fiona wiped out the power grid, but people on the island are facing another devastating emergency: How to access clean water?

With no electricity, there's no power to run filtration systems and no power to pump water into homes. That means no clean water for drinking, bathing or flushing toilets.

As of 10 a.m. ET on Tuesday, more than 760,000 customers of the Puerto Rico Aqueduct and Sewer Authority had no water service or were suffering significant interruptions, according to the government's emergency portal system.

AAA, as Puerto Rico's water agency is called, is the only water company on the island and serves 1.2 million clients, which means only 40% of households currently have clean running water. AAA President Doriel I. Pagán Crespo explained that in addition to the power outages, water supplies have been severely impacted by the flooding and surges of Puerto Rico's rivers.

"Most of the rivers are too high," Pagán Crespo said during an interview with WKAQ 580 AM on Monday, El Nuevo Día reported.

"We have 112 filtration plants, and most of them are supplied from rivers. ... As long as the rivers continue to decrease in level and it is safe for our personnel to carry out cleaning tasks, that is how we will be doing it," she added.

When the monster Category 4 Hurricane Maria slammed into Puerto Rico in September 2017, it took months to restore municipal water services, forcing people to rely entirely on bottled water or for those more desperate, to bathe and drink from natural sources that had raw sewage flowing into them. The Associated Press reported that a month after the storm, 20 of the island's 51 sewage treatment plants remained out of service. Meanwhile, Environmental Protection Agency officials could not inspect some of the island's highly toxic Superfund sites that were knocked out of service.

Even a year later, a Washington Post-Kaiser Family Foundation survey found that 50% of Puerto Ricans reported their households could not get enough clean water to drink.

For now, those communities whose water has been restored are under a boil-water advisory.