Officials at the National Zoo in Washington said two Sumatran tiger cubs were born at the facility, a major step for the endangered species. The zoo said first-time mother Damai gave birth to the first cub about 6:15 p.m. Monday and the second followed around 8:23 p.m. Officials said the cubs appear healthy and can be seen on the zoo\'s live webcams until they go on display to the public late in the fall. The zoo said the births were a major step forward for Sumatran tigers, which are endangered with fewer than 500 living in the wild. \"It\'s taken more than two years of perseverance getting to know Damai and Kavi and letting them get to know each other so that we could reach this celebratory moment,\" National Zoo biologist Craig Saffoe said. \"All I can do is smile because the team has realized our goal of producing critically endangered tiger cubs. Damai came to us as a young tiger herself, so it\'s really special to see her become a great mom.\"