SAN JUAN: Some 70,000 people have been ordered to evacuate their homes after a rain-swollen dam in Puerto Rico failed in the latest disaster caused by Hurricane Maria, which was on Saturday expected to head into open waters, reports AFP.

With the storm death toll standing at 33 across the Caribbean, Puerto Rico's National Weather Service issued a flash flood warning for people living along the Guajataca River in the northwest of the island, saying an earthen dam there was in danger of collapsing. "All Areas surrounding the Guajataca River should evacuate NOW. Their lives are in DANGER!," the NWS tweeted on Friday, saying flooding had already begun downstream.

Governor Ricardo Rossello also issued an order for 70,000 people living in the area to flee.

Public safety chief Hector Pesquera said a drain which normally releases water from the dam in a controlled fashion had stopped working, the El Vocero daily reported.Footage from WeatherNation TV showed water gushing  down a ramp-style conduit, washing away huge chunks of soil from the grassy green slopes of the dam.

Early on Saturday, the NWS extended the warning to the western Quebradillas and eastern Isabela areas, home to another 8,000 people. Puerto Rico was already battling dangerous floods after Hurricane Maria hit early Wednesday, devastating the Caribbean island. Rossello has called Maria the most devastating storm in a century after it destroyed the US territory's electricity and telecommunications infrastructure.

So far, a preliminary assessment said 13 people had died as a result of the storm, he told CNN.

"Right now our efforts are to make sure we have everybody safe, that we can rescue people. Our efforts have already produced almost 700 rescues so we're clearly focused on that."