Bridget Foy's restaurant, a fixture on South Street for nearly 40 years, went up in flames in a two-alarm fire early Wednesday.

The fire apparently started in the basement and spread quickly through the building at Second Street, on Headhouse Square.

Three firefighters were treated for minor injuries.

The first call came in about 1:15 a.m. and arriving firefighters found smoke showing from the first floor.

The blaze went to a second alarm at 2:15. About 100 firefighters and 45 pieces of equipment responded to battle the flames.

Fire Commissioner Adam Thiel said firefighters started an interior attack on the fire but had to abandon the building because of the danger of a ceiling collapse. "It was too dangerous to stay," Thiel said.

Firefighting efforts then shifted to putting out the blaze from outside and protecting adjoining structures, he said.

The fire was declared under control at 3:51 a.m., but firefighters remained at the scene for hours spraying water into the smoldering building.

The restaurant was closed when the fire broke out and investigators were speaking to and seeking witnesses who might help them determine the cause of the fire, Thiel said.

A Fire Department spokeswoman said Wednesday evening that it was too early to determine the cause of the fire.

Eleven residents were displaced by the fire and two dogs inside Doggie Style, an adjoining groomer's shop, died from smoke inhalation, officials said.

Before the morning was over, demolition equipment began tearing down the remains of the restaurant's one-story section.

John Foy opened the restaurant in February 1978 under the name East Philly Cafe, but renamed it after his daughter Bridget when she was born in 1982. Current fare included fish tacos, burgers, wings, meatloaf sliders, mussels, steak, chicken, and mac and cheese.

One constant at Bridget Foy's was change – periodic renovations kept things reasonably fresh. The food, with a slight Irish leaning, kept up with the times. Another constant was the covered outdoor patio that faced Headhouse Square and ran the length of the South Street frontage, affording patrons some of the best people-watching on the bustling street.

In its earlier days, it was a hangout for pro athletes. But even as its star faded and it settled into the life of a neighborhood mainstay, it remained relevant for weekend brunch or drinks at the bar.

Restaurant regulars Alan Romisher, 60, and fiancee Shari Fogel, 55, stood outside weighing the scene at the smoldering building where they had had many meals and drinks over the years.

"We are just heartbroken, and we hope to see them come back stronger," said Romisher, who lives nearby. "It was like an extension of our family."

"Lovely family," Fogel said of the Foys.

Michael Harris, executive director of the South Street Headhouse District, spoke of the place Bridget Foy's has held in the neighborhood in a statement.

"Bridget Foy's has been the cornerstone of South Street for 40 years and a vital part of our colorful and vibrant South Street story — and an important part of Philadelphia's history," he said. "Families from around the city, region and country have come through Foy's doors to find a wonderfully warm welcome and exceptional hospitality from this beloved family (and their staff). Foy's is a special tradition for Thanksgiving, Christmas and Easter and so many other special occasions."

Harris said the district was looking at ways to help the Foys and Howard Nelson, owner of Doggie Style.

Michael Waxman, who works as an associate broker at Plumer & Associates on South Street, a half-block away from the restaurant, remained at his Mount Airy home Wednesday morning after receiving a 6:30 a.m. email from Mona Plumer, president of the real-estate company, telling him of the devastating news.

"It's a loss," Waxman, 68, said of the fire.

"Through the years, the agents, regularly after work, we'd go down to Bridget Foy's for drinks, appetizers," he said. "People from Plumer's would always spend a lot of time there."

Waxman said he has worked as an agent at Plumer for 20 years. The real-estate office, on the 200 block of South, wasn't damaged by the fire, he said.

"Nothing takes me back to my childhood more than a grilled cheese sandwich and tomato soup at Bridget Foy's," he said, noting that the "real comfort food" at the restaurant reminded him of his mother's cooking.

The Foys and their restaurant "were a very stabilizing presence on South Street through the years," he said.

Staff writer Michael Klein contributed to this article.