CAIRO » The police arrested the girls, interrogated them for hours and then strip-searched and detained them for 10 days. They were charged with serious crimes, including endangering national security, for what the authorities regarded as an act of subversion: passing out yellow balloons.

The yellow was intended to symbolize Rabaa al-Adawiya, a square in Cairo that became the scene of a mass killing after security forces fired on protesters in August while trying to break up an Islamist sit-in. The girls, among them one whose brother died in the square, were distributing the balloons in the city of Ismailia last month in a show of solidarity with the victims.

"They are afraid of anything that reminds them of Rabaa," one of the girls, Roqaya Saeed, 17, said of the Egyptian authorities. "A black spot they can’t erase."

Memory has become a frequent casualty of Egypt’s politics since the uprising against former President Hosni Mubarak in 2011. Leaders have tried to wipe away histories of atrocities by foot-dragging on investigations until new bloodshed dulls memories of the old. But nothing so far has matched the effort by the military-led government and its supporters to extinguish the memory of Rabaa al-Adawiya, the site of the worst mass killing in Egypt’s modern history, and a dangerous reminder of absent justice and Egypt’s festering political feuds.

The traumas multiply, clouding Egypt’s path forward. Other countries with similar legacies of authoritarianism or widespread police abuses "had transitional justice before they were able to turn the page," said Ahmed Ezzat, a human-rights activist, who said that such a process would involve trials for perpetrators, truth commissions, reparations for victims and the reform of corrupt institutions.

But none of Egypt’s leaders possessed "the political will" to confront the abuses, he said.

Instead, reminders of the past have become a threat. Athletes have drawn outrage and censure for displaying the four-finger Rabaa symbol — Rabaa means "fourth" in Arabic — at competitions. For its part, the military quickly transformed the square where as many as 900 people were killed, leaving no hint of the violence except the bullet holes in lampposts and homes.

The bloodied roads have been covered with fresh asphalt, and the charred Rabaa al-Adawiya mosque that gives the square its name has been repainted in eggshell white. Paving stones that were hurled in protest have been replaced. Young shrubs brighten the place.

In a statement about its extensive work in restoring the square, the military said it had constructed a fountain and "memorial" in a place that it acknowledged had "witnessed the most difficult periods in Egypt’s history." But the memorial — a minimalist sculpture depicting two hands, representing the army and the police, cradling an orb that is supposed to represent the people — seemed to revise history rather than confront it.

"They did it so quickly," said Rabaa Abo Salma, 27, who lives near the square. "To make it look like nothing happened."

There has been talk about, but no movement on, a government investigation into the violence, which occurred at a sit-in by supporters of former President Mohammed Morsi, who was ousted by the military in July. The work has been left to the semiofficial National Council for Human Rights, which has no power to compel officials to testify.

Ragia Omran, a council member, said they had started to interview witnesses and review videos of the violence. She said she had faith there would be justice, eventually. "It will happen later on," she said.

In the meantime, the country has not even been able to agree on the final death toll. The authorities have released conflicting figures, saying that between 683 and 1,000 people, including 43 police officers, were killed across the country on Aug. 14, the day the sit-in was stormed. Morsi’s Islamist movement, the Muslim Brotherhood, has released figures widely seen as inflated, claiming that thousands died. Other reports have put the number at between 800 and 900 people.

There is little clamor for any inquiry among the public, which harbors deep antipathy toward the Brotherhood and seems desperate to move on from Egypt’s era of protest. Despite a crackdown on the movement, Morsi’s supporters have continued to march. They have adopted the name of the square as their slogan, and the four-finger symbol that has become its own provocation.

In recent weeks, two Egyptian athletes have ignited controversy after flashing the symbol at sporting events, a gesture, they said, to the people who died. One of them, Mohamed Youssef, who wore a Rabaa T-shirt as he was receiving a gold medal at a kung fu competition in Russia, received a yearlong suspension from competition by Egypt’s Kung Fu Association, according to local news media.

On Sunday, a soccer player, Ahmed Abd el-Zaher, flashed four fingers after scoring a goal for his club, Al Ahly, shortly before it won the African Champions League title. Egypt erupted in jubilation over the victory, but Abdel el-Zaher was suspended from playing with the club, which on Tuesday announced that it would transfer him.

Since the uprising almost three years ago, anniversaries of serious abuses come and go, without justice or recognition for the victims. Instead, they are memorialized with graffiti, which the authorities periodically try to erase. Next week, activists are expected to commemorate the anniversary of demonstrations two years ago that ended with the deaths of 45 protesters.

To date, only one police officer has been prosecuted in those deaths.

Morsi appointed a fact-finding committee to investigate protesters’ deaths after the uprising, but never publicized the panel’s report, which was said to implicate the military in abuses. "It contributed to hiding the truth," Ezzat said. "A buried report is as good as thin air."

Heba Morayef, of Human Rights Watch, said Egypt’s "short memory" had gotten progressively worse throughout its stormy transition. "People have forgotten the rights of the martyrs," she said. "The only people who keep fighting are the mothers, the families of the victims and the lawyers."

Rabaa al-Adawiya led to forced amnesia.

"The state is taking it to a whole new level of denial," Morayef said, noting that Egypt’s interior minister said in a television interview soon after the violence that only 40 people had been killed, even as the government’s Health Ministry was putting the early toll at close to 300 people.

The local news media have largely fallen in line with Egypt’s military-backed government, relieving pressure on officials to investigate, or at least acknowledge, the magnitude of the killings, Morayef said.

Memories are sharper among the people who live and work in the square. Mahmoud Rizk, who runs a nursery there, remembered spending Aug. 14 on the phone with his brother, who was trapped in a hut in the nursery during the fighting.

From the look of the place, it was a miracle that his brother survived. Bullets struck the hut from two sides, shredding metal on the bunk beds where the workers slept. After the fighting had died down, soldiers came with dogs to search for the bullet slugs and remove them.

"It will be a black spot forever," Rizk said.

© 2013 The New York Times Company