Correction: The article about the birth of a panda cub at the National Zoo misstated the time of birth. The cub, which has since died, was born Sept. 16 at 10:46 p.m., not 10:26 p.m. This version has been corrected.

Keeper Becky Malinsky was getting ready for bed Sunday, sitting on the couch with her dog when she decided to check the National Zoo’s panda cam, which was monitoring Mei Xiang, the female giant panda.

Malinsky knew that Mei was nearing the end of her annual reproductive cycle, and that most experts figured, after five failed attempts to impregnate the panda, the odds of having a new cub at the zoo were almost nil.

But Malinsky decided to check anyhow. She fired up her laptop and logged on to the camera that had been intently trained on Mei for the past few weeks. She couldn’t see much, but she could hear the panda panting. She also heard a strange squeaking noise in the background.

Maybe there was something wrong with the camera, she thought. She logged off, and logged back on again. The squeaking continued. Then it hit her. This wasn’t a glitch. These were the squeals of a cub.

Thus, heralded by a cry like that of a squeezed tub toy, did Washington learn that seven years after the birth of the zoo’s only surviving panda cub, it had another on which to lavish its prodigious affection.

The birth transforms the zoo’s multimillion-dollar giant panda research project, guarantees that Mei will remain in Washington for several more years and gives scientists an unexpected panda reproduction surprise to ponder.

“This is one of the best of things that can happen to Washington right now,” zoo director Dennis Kelly said.

The zoo said the panda house has been closed and will probably remain so for several weeks. The cub, which keepers said probably weighs about four ounces and is quite fragile, will not make its debut for several months.

Experts said they do not yet know the sex of the cub, and won’t for about a month, when they have a chance to examine it. Kelly said the zoo will abide by the Chinese custom of waiting 100 days before naming the cub.

He said that residents of the metro area will have a say in the naming, however.

“It’s important for Washington,” Kelly said.

Zoo officials, intensely focused on panda reproduction, had been vocal about wanting Mei replaced if she did not have a cub this year.

And they were ready to open replacement talks with China, which owns and leases all giant pandas.

Malinsky, who was off duty, already had checked Mei on the panda cam a half-dozen times over the weekend. She said she has been working with the giant pandas for about five years.

“We knew that if she were to have a cub, we were nearing D-Day,” Malinsky said, even though zoo experts were predicting that those chances were probably less than 10 percent, given the previous failures.

On Sunday, “something just said, ‘Let me check on Mei before I go to bed,’ ” she said.

When Malinsky realized what she heard, she was “blown away,” she said. “It was like a miracle.”

She grabbed her cellphone and began texting co-workers. “If you guys are awake, there are strange noises coming from Mei Xiang’s den,” she said she texted.

She then telephoned the zoo’s veteran panda keeper, Laurie Thompson, and said: “You’re not going to believe this. You need to turn on your computer. There’s a cub.”

After Thompson concurred, Malinsky said: “Laurie, I’m shaking. Are you? She said, ‘Yes!’ ”

As the news spread Monday, zoo officials hugged and high-fived, TV crews gathered at the Smithsonian facility on Connecticut Avenue in Northwest Washington and at least one panda lover wept with joy.

“I’ve been crying all day,” said Holly O’Brien-Yao, 58, of Falls Church as she stood outside the roped-off panda compound just before noon. “I’ve been praying for something really wonderful to happen to me, and this does it.”

Anthea Higgins, 43, of Potomac, who was visiting the zoo with her children, Sean, 8, and Caroline, 6, said the panda birth was a “spectacular” happening.

In a chaotic world, “it’s a little piece of hope,” she said.

At a noontime news briefing, zoo officials said they have closed the panda house to let mother and cub bond in peace and quiet. The cub was born at 10:46 p.m.

The birth will probably ignite a fresh wave of panda mania, two years after the zoo’s beloved first cub, Tai Shan, who was born in 2005, was sent to a breeding program in China.

All cubs and adult pandas, in the United States by agreement, are the property of China.

Zoo scientists were not sure why Mei, 14, became pregnant this year.

She had been artificially inseminated April 29 and 30 after she and Tian Tian, the zoo’s 15-year-old male, failed to mate on their own.

Pierre Comizzoli, a zoo reproductive physiologist who performed the procedures with a Chinese colleague, said he used sperm from Tian Tian that had been frozen and stored.

It was from the same batch that delivered Tai Shan.

Comizzoli said he had been part of the team, directed by the late zoo reproduction scientist JoGale Howard, that assisted with the 2005 pregnancy done via artificial insemination but with fresh semen.

He noted that this year Mei went into heat in April, when giant pandas usually do so, instead of mid-winter, when she had inexplicably gone into heat the previous three years.

The zoo announced Aug. 20 that Mei had entered the final phase of her annual reproductive cycle — one that would conclude in 40 to 50 days, with or without a cub.

It is notoriously difficult to determine whether a giant panda is pregnant because the animal can exhibit many false signs.

In its quest for cubs, the zoo has focused intense research on panda reproduction. In December, local philanthropist David M. Rubenstein, co-founder and managing director of the Carlyle Group, a global asset-management firm, pledged $4.5 million to fund such research.

On Sept. 5, the zoo announced that it was getting an additional $400,000 from the Ford Motor Co. Fund to study panda health. Much of the funding will go toward upgrading the 18-year-old panda-cam system, the zoo said.

Last year, Chinese and U.S. officials agreed to extend the adult pandas’ stay in Washington for five years. The deal replaced a 10-year lease that expired Dec. 6, 2010. The new agreement expires Dec. 6, 2015.