The bright-red signs took up the entire side of the two trash cans and read in large lettering: “BALLOT BOX.”

It was an advertisement unveiled Friday for the Union League Legacy Foundation’s exhibit on the history of voting rights — and a quickly realized mistake.

The signs were up for only a couple hours, said Kira Foley-Tuzman, the foundation’s chief administrative officer, before the group realized that the signage could mislead voters into thinking a trash can was an official ballot box.

It was an unfortunate messaging blunder, with terrible timing.

People on social media had derided the ad as an attempt to confuse voters during an election in which Pennsylvania and Philadelphia have become the subject of the president’s attacks on the security of voting by mail.

» READ MORE: Trump has put Philly on the front lines of his attack on voting

There was at least one complaint to the District Attorney’s Election Task Force, a spokesperson said. The task force told the foundation to remove the advertisements immediately to avoid any possible confusion with actual ballot boxes.

“It was certainly not intended,” Foley-Tuzman said of the misleading advertisements. “We immediately took them down and have been communicating nonstop to folks.”

The Streets Department deployed sanitation workers to sort through the trash of those bins — at Broad and Sansom Streets and 15th and Sansom Streets — looking for any ballots a voter may have slipped in. A city spokesperson confirmed there were none.

“Crisis averted,” said David Thornburgh, CEO of the Committee of Seventy, a nonpartisan advocate for trustworthy government in Philadelphia and Pennsylvania.

His organization has been educating voters about new procedures, especially about mail-in voting and where to drop off ballots this election. As of Friday, more than 407,000 Philadelphians had requested general election mail ballots.

» READ MORE: Everything you need to know about voting by mail, or in person, in Pennsylvania

“Even if one ballot ended up in that trash receptacle rather than where it belonged, that’s just a huge shame,” Thornburgh said. “All eyes are on Philadelphia. And for six months we’ve been trying to do everything we can to educate voters, and ensure that we execute a fair, safe and secure election. So, we don’t need this.”

President Donald Trump has attacked voting, targeting Pennsylvania, a swing state with 20 Electoral College votes that could decide the election, and Philadelphia. His campaign surveilled and videotaped voters dropping off ballots last week at City Hall. During the first presidential debate, he made false claims about poll watchers, saying: “Bad things happen in Philadelphia.” And, his campaign filed a lawsuit against the city over being able to observe activities inside satellite election offices.

Omar Sabir, one of the three Philadelphia city commissioners who oversee elections, said he understood why people would have strong reactions to the trash can “ballot box” advertisements and emphasized that voting in Philadelphia is safe.

“There is a lot of confusion going on right now with ballot boxes and there’s, let’s be quite frank, people are doing tricks right now, they’re doing voter suppression right now. So people were concerned," Sabir said.

The foundation posted a formal apology on Facebook and encouraged people to visit its "Ballot Box: America’s Fight for the Vote” exhibit on the history of voting rights.

“The biggest message,” Foley-Tuzman said, “would be go vote. Be active and engaged and responsible citizens.”

The exhibit previously advertised on the trash cans is open to the public at the Union League, 140 S. Broad St., through June on Tuesdays and Thursdays, from 3 p.m. to 6 p.m, and on the second Saturday of each month, from 1 p.m. to 4 p.m.