"You're here for your own protection," the interrogator told Said Haddadi, a French national who was swept up in a wave of detentions of human rights activists and journalists during deadly clashes between pro- and anti-government protesters.
Dozens of activists who were rounded up in Egypt's chaos like Haddadi have been freed, but some are believed to remain in custody. Advocates say the government refuses to release names or locations of detainees, and the involvement of both police and military agencies makes it hard to determine who is responsible.
"It's not clear who is doing what," said Sally Sami of the Cairo Institute for Human Rights Studies.
On Sunday, Egypt's Vice President Omar Suleiman met opposition figures and promised to begin releasing political detainees as part of a concession package. Spokesman Magdy Rady said Egypt was in such a state of upheaval that "some groups" might be detaining people "in the name of the government" without proper authority.
"In the mess we are in, everything is possible," said Rady, promising investigation into such cases. "We are really against these forces now."
Al-Jazeera's English-language news network said one of its correspondents was detained Sunday by the Egyptian military. The report said Ayman Mohyeldin, an American citizen, was taken Sunday from Tahrir Square, where protesters demanding President Hosni Mubarak's ouster are holding out. He was released after seven hours, the channel said.
There are no reliable figures for the number of people detained after protests began Jan. 25 in Cairo and grew into an uprising that pushed Egypt into crisis. The raids on activists - some were reported Saturday - were a targeted backlash by security forces despite the government's pledges of reform.
The military role in arrests, in particular, is seen by government opponents as ominous because the armed forces, a pillar of state authority, have sought a neutral image in the conflict and would be key to a smooth transition of power.
"The problem is that the army doesn't have any justice system, they don't have any way to process these detainees," said Peter Bouckaert, emergencies director at the New York-based Human Rights Watch.
One of the most prominent activists believed to be in detention is Wael Ghonim, a Google Inc. marketing manager who took part in protests against Mubarak's rule. He was reported missing on Jan. 27.
On that day, he was apparently circumventing a government shutdown of the Internet - a post on a Twitter account listed under his name said: "Very worried as it seems that government is planning a war crime tomorrow against people. We are all ready to die."
A YouTube video of a street protest shows the detention of a man resembling Ghonim. In the footage, men in plainclothes approach a line of protesters and grab the man identified as Ghonim, hustling him through a gap in a squad of riot police.
Haddadi was among several dozen activists who were detained Thursday at the Hisham Mubarak Law Center and transferred to what they believe was a military police camp on the outskirts of Cairo. As they were led from the law office to a van, a crowd of pro-government supporters screamed insults and spat at the vehicle.
The crowd's message was "we are traitors and we sold the country for money and we are agents of the Israelis and we want to create havoc in the country," Haddadi said as he described the encounter after his release Friday night.
In detention, the group slept in the open air, within the walls of a compound, and each was occasionally given a piece of bread with jam or honey. Guards removed their blindfolds when they went to the bathroom.
Interrogations were cursory, and Haddadi said he was not harmed, in contrast to numerous reports of torture and other abuses in Egyptian detention facilities over the years. He was dropped off at a hotel closed for renovations near the airport, and all others in the group were eventually released.
Security forces, however, ransacked offices and removed files from the law center, headquarters for groups that provided legal aid for protesters and gathered data on alleged abuses, said Hassiba Hadj Sahraoui, Amnesty International's deputy director for the Middle East and North Africa.
"All the hard drives of all the computers were taken," Sahraoui said in a telephone interview from London. "It's not clear whether there is backup of all that information."
She said the raid was similar to one conducted by Iranian authorities on a human rights center set up by reformist leader Mehdi Karroubi around the time of anti-government protests in Tehran in 2009.
One Egyptian rights group, the Nadim Center, reported a fresh round of detentions on Saturday, including several people who were taken from their homes and offices.
Before Egypt's uprising, rights groups followed a standard procedure when someone was detained, filing a complaint at the public prosecutor's office. Sami of the Cairo Institute for Human Rights Studies said the situation is now chaotic, citing the case of a person who was held for nearly a week without activists being aware of the case.
"Egypt is a big country, Cairo is a very big city," she said. "We don't necessarily get reports of each and every detention that takes place."