Authorities in Puerto Rico rushed today to evacuate tens of thousands of people living downriver from a dam said to be in danger of collapsing because of flooding from Hurricane Maria. The 1920's era earthen dam on the Guajataca River in northwest Puerto Rico cracked yesterday, prompting the government to issue an order for 70,000 people in downstream towns to evacuate. The local office of the National Weather Service warned last evening of an imminent dam break.<br/>'<br/>A Puerto Rican government official confirmed that evacuations were continuing.He said the dam had cracked under the weight of so much flooding, sending water gushing through and prompting fears of flash flooding.<br/><br/>Puerto Rico was already battling dangerous floods elsewhere on the island because of Hurricane Maria, which hit before dawn Wednesday as part of its furious tear across the Caribbean.<br/>'<br/>Governor Ricardo Rossello visited Isabela, an area near the dam, late yesterday and urged people to get out. <br/><br/>