The National Zoo’s giant female panda Mei Xiang gave birth to a cub on Friday. (The Washington Post)

The National Zoo’s female giant panda gave birth Saturday night to a second cub, but it was stillborn, the zoo said. The stillbirth occurred about 26 hours after Mei Xiang had given birth to a live cub.

The zoo said keepers watching Mei Xiang on a panda cam saw her groom the stillborn cub for 17 minutes. But after the grooming stopped, the stillborn cub fell from the mother’s body onto the floor of the den, where it lay, without sound or movement.

Through this period, the zoo said, staff members could see the silent second cub, and hear the squeals of the cub that was born Friday.

That cub “continues to do well,” a zoo spokeswoman said by e-mail about 11 p.m. Saturday.

Equipment described as a “grabbing device” was used to retrieve the second cub. The zoo said it was evident at once that the cub had developmental abnormalities.

It was not fully formed and was never alive, the zoo said.

A necropsy, similar to an autopsy, was under way Saturday night, according to t he zoo.

Earlier Saturday, panda keepers had tried to take the first cub from its mother’s grasp for a brief but crucial physical exam.

They call it the grab, a gently choreographed and dangerous procedure. It’s never been done at the Smithsonian National Zoo.

On Saturday, a team of keepers, curators and veterinarians tried it for the first time.

The plan was for one keeper to distract Mei with honey, sugar cane and a pear while another keeper took the cub from her and handed it to a veterinarian.

After a quick once-over — a check of weight, length and general health — the cub would be returned to its mother.

The team tried once Saturday morning but couldn’t distract Mei. She sniffed at the pear but stayed focused on the cub, which she kept cradled under her chin.

“It’s not in a position where we feel safe to grab it,” said panda keeper Marty Dearie, who was on the grab team. The keepers, who were just a few feet from the panda, behind protective bars, backed off.

“There always is a danger when you’re around an animal that weighs 240-some-odd pounds and has a jaw that can break a piece of bamboo,” he said. “She is an animal that can cause damage if she needs to.”

In addition, the cub is small and delicate and can neither see nor hear. “We don’t want to startle Mei and make her do something, maybe, to the cub,” Dearie said. So, until everything is perfectly safe, “we just won’t do the grab.”

Plus, “I’ve never grabbed a cub before,” he said..

A second attempt in the afternoon also fell short. Dearie said Mei seemed a little more interested in the food and that the cub was “still very active, very vocal.”

He said the team will try again Sunday.

The moves came as the zoo and the Washington region were abuzz over the first cub’s birth Friday — an event that was broadcast live on the zoo’s new high-definition panda cams.

The cameras captured Mei Xiang’s labor and, at 5:32 p.m., the delivery of the robust, loudly squeaking cub. Dearie said it looked like a small, pink rat covered in white fuzz.

For a time, the zoo had kept a vigil for the possible birth of a second cub. Pandas frequently have twins. But about six hours after the birth, the zoo came to think that a twin probably wasn’t coming.

By Saturday night the staff “really believed” that the window had closed, a spokeswoman said.

The mother and the first cub were both reported to be doing well earlier Saturday, but zoo director Dennis Kelly said, “We’re going to be tense for a while.”

Since the death at the zoo last year of a newborn cub, zoo experts resolved to examine early on to head off possible trouble.

The zoo had traditionally avoided such interventions to allow mother and cub to bond naturally. And Mei Xiang did so with her previous cubs: Tai Shan, who was born in 2005, and the cub that died six days after its birth in September.

In Tai Shan’s case, keepers didn’t physically check him for about 30 days, the zoo said. He was sent to a breeding program in China in 2010.

In last year’s emergency, keepers extracted the cub with tongs, but Mei was readily distracted and the cub was probably already dead, the zoo said.

“Based on the fact that [last year’s] cub had some issues . . . we just said, ‘You know what? Let’s think about getting our hands on it earlier,’ ” he said. “The idea is: Let’s just make sure everything’s going really well, and then give it back to her and let her do her thing.”

The zoo had sent Dearie and a fellow keeper to China this month to study how cubs there are taken from their mothers, the zoo said.