TORONTO - The Toronto Zoo says two giant panda cubs born about eight weeks ago have now partially opened their eyes.

The zoo says the cubs -- who were born blind -- are now sensitive to light and darkness, and are continuing to grow.

The two baby pandas are also developing stronger voices, with the zoo saying their quiet squeaks have become stronger squawks.

The zoo notes it is still a very critical time for the pair.

The cubs and their mother, Er Shun, are housed in a maternity den which isn't open to the public.

Er Shun is on loan from China. She and a male panda named Da Mao arrived in 2013 and are slated to move to the Calgary Zoo in 2018.