After a thorough examination, the three Sumatran tiger cubs born at the San Francisco Zoo on March 6 were finally given a clean bill of health.

The three cubs, all male, were found to weigh from 4.2 pounds to 4.8 pounds when examined by the veterinarians Saturday, the San Francisco Chronicle reported.

According to Jacqueline Jencek, the zoo’s chief veterinarian, Sumatran cubs have a 30 percent to 40 percent mortality rate, and the rate is higher with first-time mothers. This is the reason why zoo stuff left the new family alone for the first several days after the births and at first only confirmed one cub was born. The other two were discovered later when, Leanne, the cubs’ 230-pound mother, got out of her nest box for a drink of water.

Leanne and her mate, George are part of the zoo-s breeding program for their endangered species. Sumatran tigers are critically endangered with an estimated 400 to 500 living in the wild and about 200 in captivity.

San Francisco Zoo was the place of a tragic attack on Christmas Day when a Siberian tiger got out of its enclosure and attacked three young men, one fatally. The police killed the tiger, named Tatiana.