The downstairs bar area at Fig + Olive restaurant in Washington. (Deb Lindsey/For The Washington Post)

At least four people have been hospitalized with salmonella-like symptoms after apparently dining or drinking at Fig & Olive, the trendy, New York-based chain that opened a location at CityCenterDC in June.

One woman was admitted to George Washington University Hospital for a second time on Tuesday after previously being admitted over the Labor Day weekend for salmonella-like symptoms, according to her longtime boyfriend, who spoke on condition that he not be named to protect their privacy. The woman was scheduled to spend Wednesday night at GW for further observation.

At least three other patients, and possibly a fourth, were admitted to Sibley Memorial Hospital over the holiday weekend with salmonella infections, according to a hospital spokesman. They had all been released, he said.

The infections are apparently all linked to Fig & Olive, where the patients had dined in late August or early September. The incubation period for salmonella can be between 12 and 72 hours, according to The Centers for Disease Control and Prevention estimate that about 450 people die annually in the United States from “non-typhoidal” salmonella. No deaths have been traced to the recent outbreak.

Ian Kitzmiller, general manager for the Washington location of Fig & Olive, said the restaurant was searching through all its products and food-handling procedures to find the potential source of the bacteria. The District’s Department of Health inspected the restaurant on Wednesday, Kitzmiller said, and “there were no issues.”

The woman admitted to GW apparently didn’t eat at Fig & Olive, according to her boyfriend. She had two glasses of champagne and water. Kitzmiller said that Fig & Olive’s water is filtered in-house and that managers have checked the dishwasher and determined it is hot enough to kill bacteria lurking in glassware.

The bacteria “would spread fast if it were in the water,” Kitzmiller added.

The restaurant also determined that one employee came in sick with a stomach bug, even though all employees have been instructed to stay home when ill. But at this point, Kitzmiller said, “nothing is being traced back to a specific source.”

Fabien Guardiola, vice president of food and beverage for the chain, issued a statement after being on site in Washington on Wednesday.

“This morning the health department conducted a full inspection of our premises,” he said. “We are not aware of any violation or risk found. In addition, we hired a third party firm to also conduct a separate investigation and assure us, our guests and the public that all appropriate and proper safety protocols were and are in place. We will continue to cooperate with all health authorities to the extent it is warranted — the health and safety of our premises is of paramount importance to us.”