Guayllabamba Zoo officials, who had been closely monitoring the incubation of a condor egg for three weeks, examined the egg and found it did not contain an embryo, the director of the Ecuadorian zoo, Juan Manuel Carrion, told Efe.

"The egg turned out to be infertile. It surprised us because ... infertile eggs are discarded by couples early and this case is unusual" since the parents "continued to care for it beyond the usual time," Carrion said.

The fledgling would have been the sixth offspring of condor couple Auki and Kawsay, and it would have joined its two small siblings, who are being kept isolated as part of a project to release them in the wild.

The normal gestation period is 60-65 days and Thursday would have been the 69th day.

Zookeepers decided to examine the egg on Wednesday and found there was no embryo.

"You always run this risk," Carrion said. "This passion for knowledge has its ups and downs."

Thousands of people had been monitoring the egg's status via an online video feed or watching in person on a screen at Guayllabamba Zoo in Quito.

"I would say that this is not an unhappy ending, but it's not the one we were perhaps expecting. We'll stay on the path, continue moving forward," the zoo director said.

The first three offspring of dad Auki and mother Kawsay were sent to rescue centers for breeding, as the condor - Ecuador's national symbol - is an endangered species. EFE