Two tiger cubs at Delhi’s National Zoological Park died just days after they were born on August 15, The Indian Express reported on Thursday. Zoo Director Renu Singh confirmed that a female cub died on August 18 and a male cub died on August 26.

The cubs were born to a white Royal Bengal tigress and a yellow-striped Royal Bengal tiger. Singh said the postmortem of the cubs revealed that the female cub developed liver cirrhosis while the other one died of gastroenteritis.

In May, the zoo facilitated mating between three-year-old white Royal Bengal tigress Nirbhaya and five-year-old yellow striped Royal Bengal tiger Karan. The last time such breeding took place at the Delhi zoo was in 1991.

“We put up CCTV cameras inside and a screen outside to monitor the activity of the cubs and the mother,” Singh said. “The cub which died on August 26 was healthy and drinking its mother’s milk. It then suddenly passed away.”

He said they were expecting a bigger litter and heavier cubs. “I haven’t lost hope though,” Singh said. “We will try again this year, for better genes.

Deputy Inspector General of National Tiger Conservation Authority Sanjay Kumar said cubs can die if recessive genes get clubbed together. “Since the cubs died so young, it could be a genetic disorder,” he said. “I suggest that a genetics analysis be conducted to understand the reason, as it can be helpful in the future. If the mother develops an infection during pregnancy, that too can be problematic for the cubs.”