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 to a cub Friday as hordes of people in this panda-obsessed realm halted work to watch the royal arrival in intimate high-definition on the zoo’s new public panda cams.

Across the area, thousands heeded the zoo’s summons to its cameras and sat at their computers, glued to the live black-and-white images as Mei Xiang gave birth to the scrawny cub at 5:32 p.m., the zoo said.

The birth sparked cautious jubilation at the zoo, salved the memory of the cub that died in September, and restored dreams of pandamania in a city that has longed for a cub since the days of the legendary Tai Shan.

As if anticipating a regal birth, the zoo sent out an alert on Twitter and Facebook after Mei Xiang’s water broke at 3:36 p.m., inviting people to watch what would ensue.

The zoo said the labor could last up to 10 hours. But the panda’s lasted less than two. The cameras captured her labor, the cub’s abrupt delivery, and Mei Xiang scooping it up and then cradling it against herself.

“We feel incredible,” said Dennis Kelly, the zoo’s director. “The team is just ecstatic. But

we’re also very cautious at this point. We look like we have a healthy cub. It’s squawking appropriately. . . . It looks like it’s a good size. So all that is so far, so good.”

The zoo said it was watching to see whether a second cub might be born because giant pandas frequently bear twins. “There’s a window that runs from two to six hours after the first birth, where we are watching carefully for a twin,” Kelly said.

As of 8 p.m., Mei Xiang was still having contractions. But as of only a few minutes before midnight, no second birth was reported.

“In the next couple of hours, we’re looking for Mom to take care” of the newborn, Kelly said shortly after the birth. “If it were premature, we would see the lungs begin to shut down. So far, none of that’s indicated. What we’re looking for is continued squealing. We’re looking for evidence that it’s nursing.”

“It’s just a very anxious time for us,” he said. “But Mei’s a good mom.”

Kelly said he witnessed the birth on the panda cam, which faltered because so many people were tuning in, he said.

The zoo said it planned a quick physical examination of the cub Saturday. One keeper will distract the mother with food, while another, wearing Kevlar gloves, will take the cub to a nearby examination table.

The zoo has not done that before, to avoid interfering with the mother-cub bonding.

But panda experts in China do it regularly, and other zoos are starting to do it to make certain the cubs are in good health, zoo officials said. Two of the zoo’s panda keepers have been studying the procedure in China for the past two weeks.

Experts will check the cub’s size, weight and body temperature and go over the body for any abnormalities.

In September, Mei Xiang gave birth to a four-ounce girl, but it died six days later. The cub had underdeveloped lungs that led to liver problems.

The zoo’s new cameras were activated just several weeks ago. As word spread that Mei Xiang had gone into labor, zoo spokeswoman Pamela Baker-Masson said: “We’re thrilled! . . . Everybody’s watching!”

The zoo had gone on a round-the-clock pregnancy watch Aug. 7 and closed the panda house the next day after announcing that Mei Xiang was starting the closing phase of her gestation period.

It is difficult to determine if a giant panda is pregnant, because it goes through the same physiological stages whether it is bearing a cub or not.

The conclusive evidence is the arrival of a cub or the close of the period with no cub.

Mei Xiang gave birth to the much-loved Tai Shan in 2005, who was sent to a breeding program in China in 2010. After his birth, Mei Xiang had five false pregnancies between 2007 and 2012.

And before last year’s pregnancy, the zoo had been talking to Chinese officials about the possibility of replacing her. China owns all giant pandas in U.S. zoos.

But her pregnancy changed things.

On March 30, Mei Xiang was artificially inseminated twice after natural breeding attempts with the resident male panda, Tian Tian, were unsuccessful.

During the first procedure, she was inseminated with fresh sperm from Tian Tian and samples collected in 2003 that had been frozen.

In the second procedure, Mei Xiang was inseminated with Tian Tian’s frozen 2003 sperm as well as frozen sperm from the San Diego Zoo’s male giant panda, Gao Gao.

The zoo said it will conduct DNA testing later to determine paternity.