Jody Della Barba got tipped off almost two weeks ago about plans to open a supervised injection site not far from her home in South Philadelphia.

Within days, Della Barba, a community activist and former secretary to Mayor Frank L. Rizzo, had confirmed the location: the Constitution Health Plaza on South Broad Street. She and others identified businesses already in the building, including a day care center and an elder care organization, then turned to Facebook to enlist neighbors to spread the news.

On Friday, they were relishing a swift and stunning victory. Barely a day after the nonprofit Safehouse, armed with a judge’s approval, had announced the South Philadelphia location, its operators had walked back plans to open the nation’s first supervised injection site. That came after intense outcry from residents and city politicians, who criticized what they saw as a lack of community input.

Della Barba said a key to their strategy was informing other businesses around the plaza that people in addiction would be encouraged to come to their neighborhood to legally use drugs — a step that she believes rattled other tenants and ultimately persuaded the site’s landlord to rescind the lease.

“When you want to go after someone," Della Barba said, "you have to hit their pocketbook.”

She and other opponents had no plans to slow their campaign. Weekend rallies were planned and city officials were mulling next steps. "We’ve got to make it illegal to put this anywhere,” Della Barba said.

In agreeing to delay, Safehouse’s leaders acknowledged failing to hold community discussions before announcing they would begin operating next week. But on Friday, Safehouse vice president Ronda Goldfein appeared to challenge complaints that residents were blindsided.

“We were trying to communicate with folks. We didn’t want this to hit people totally by surprise, we were trying to have conversations," she said, adding that ongoing legal battles limited what they could say. Still, she said, the flow of social media suggested the site wasn’t a secret. "How would the location have been shared in the community if people in the community didn’t know about it?”

Bordered by Mifflin and McKean Streets, the Broad Street site is surrounded by banks, stores and other businesses. It’s around the corner from a day-care center, a block from the Melrose Diner, and a five-minute walk from the East Passyunk Avenue corridor lined with restaurants.

Supporters of supervised injection sites say they protect public health and help prevent overdoses, keeping people alive until they can go into recovery, and noted that sites in Canada and Europe have not attracted drug dealers or people in addiction to the area. Mayor Jim Kenney has said the site could save at least dozens of lives each year in Philadelphia, which has logged more than 3,000 fatal drug overdoses in three years.

But City Council united against the site and also helped mobilize opposition.

Councilmember Kenyatta Johnson said he first heard about Safehouse’s plan to open at Constitution Health Plaza — within his district — on Feb. 21, four days before the official announcement.

“I was informed that they were already staffed up. If they were already staffed up, that means this process had been prepared for — it had to be taking place back behind the scenes," Johnson said. He met Tuesday with Managing Director Brian Abernathy to discuss the operation but expected there also would be a neighborhood meeting.

“Something of this magnitude that affects everyone should be rolled out in a very public way with community input, so people can just know what are the facts," he said.

Meanwhile, concern about how the injection site might affect homes, schools, and businesses spread quickly among neighbors. A petition against safe injection sites in Philadelphia garnered 6,870 signatures. Rallies were planned.

Leighanne Savloff, a 43-year-old mother of two who lives in the Girard Estates neighborhood, said the opposition spread like wildfire on Facebook.

“Because we do live in that close, tight-knit community, it goes viral amongst us,” she said.

The community was already upset about a recent increase in crime; she called news of the supervised injection site “the straw that broke South Philly’s back.”

As organizers like Della Barba posted phone numbers, people encouraged each other to flood politicians and building owner Steve Atlass with calls.

Some Facebook commenters attributed their opposition to a South Philadelphia heritage unwilling to be steamrolled by city government. “People should NEVER UNDERESTIMATE OUR SOUTH PHILLY COMMUNITY!!!!” one woman wrote.

Councilmember Mark Squilla said he believed concerns from the Constitution Health Plaza tenants contributed to the suspension of the plan. “It was a combination of a lot of different things," he said.

Constitution Health Plaza apologized to tenants in a letter, saying it had hoped “to play a positive role in providing an innovative way to bring needed services to those suffering from addiction” but that it had listened to community concerns.

“We believe in the good intentions of all involved — on both sides of this issue — and want to thank you for your honest communications with us over the past few days,” the letter said.

Johnson said he has not heard that Safehouse is considering any other property in his district, but he would oppose efforts to open somewhere else.

Business owners near Constitution Health Plaza said Thursday’s announcement eased their worries that the site would hurt their business.

“The community felt disrespected,” said Joey Maccarone, who lives in the neighborhood and works as a chef at Pizzeria Pesto on Broad Street, across from the site.

But some did voice support for the site or challenge neighbors’ opposition, and supporters in the community said they hoped to rebuild trust.

“I see so much support in South Philly,” said Brittany Salerno, a community outreach worker in the neighborhood who works with homeless people in addiction. “And unfortunately of course there are community members that feel blindsided and they’re so angry about how this happened that they don’t want to hear the rest of it. But there’s so much ample support.”

Staff writers Sean Collins Walsh, Laura McCrystal, and Aubrey Whelan contributed to this article.

Ronda Goldfein of Safehouse is the wife of David Lee Preston, an editor at The Inquirer. He is not involved in coverage of this story.