After two days of deadly clashes, violent backers of Mubarak were mostly absent Friday from Tahrir Square, scene of huge protests against Egypt's autocratic leader. As in the past, they enjoyed at least tacit approval from the state, or elements of it, disbanding as quickly as they formed.
"The people we found on the streets are incredibly familiar to us," said Hossam Bahgat, founder of the Egyptian Initiative for Personal Rights, a non-governmental group. "They have always been used or employed to do the dirty business of the government or police."
The Mubarak government rejects accusations that it orchestrates brazen assaults by gangs with no formal affiliation in an apparent effort to distance the state from direct responsibility. It denied involvement in the fighting at Tahrir Square, but apologized, acknowledging signs that it was "organized" and promising an investigation.
This two-track approach - denial and a pledge to get to the bottom of the violence - reflects the contradiction of Mubarak's rule over nearly three decades. While Egypt holds elections, crackdowns and allegations of vote-rigging render them invalid for those who want new leaders.
The thugs who seek to enforce government authority are a separate group from Egyptians who peacefully support the president.
In November, pro-Mubarak men stormed polling stations, scaring off voters as police stood by. During 2005 elections, suspected security officials in plainclothes beat demonstrators and journalists, and there were reports of sexual assaults on female protesters.
During parliamentary elections in 2000, many voters complained that plainclothes police tried to pressure them into revealing their political allegiance in order to let only supporters of the ruling National Democratic Party into polling stations.
Security officials deny taking sides, blaming political partisans for such unrest. But the spectacle of thousands of Mubarak backers armed with firebombs, knives and whips converging on Tahrir Square Wednesday without military intervention suggested a degree of collaboration with the state.
"We have orders not to leave here," one man in the crowd was overheard saying on his cell phone. He spoke quietly and moved away when he realized someone was close enough to hear.
The Mubarak partisans tended to be heavyset men in their 30s or 40s, in contrast to anti-government protesters who come from a broad range of ages and backgrounds. Some of those involved in election attacks were believed to be thugs hired for the day, and there were similar, unconfirmed allegations in the latest attacks.
Bahgat said he first saw pro-Mubarak supporters gathering Tuesday evening around the heavily guarded state television building, a key installation that broadcasts pro-government messages. There were a few hundred, some assembling signs with slogans.
"We thought that this was just a media stunt to show that not everyone on the streets is pro-democratic," he said. "What came as an utter shock to us was the decision of the army to allow them access to Tahrir Square."
Bahgat said "anecdotal evidence" indicates ruling party officials and lawmakers, as well as neighborhood officials, may have had a role in organizing the pro-Mubarak group. But he said there was no sign that the crowd received "clear instructions" from any government office or police department.
"There are a lot of forces playing in this mess, in this chaos," government spokesman Magdy Rady said in a denial of state involvement. "Who is igniting all this?"
The level of organization of the pro-government attackers remains difficult to pinpoint, amid a swirl of conspiracy theories.
On Friday, in a sign of the skittish mood, several soldiers walked across Tahrir Square, drawing cheers from protesters. Elsewhere, sections of the throng concluded the cheer meant Mubarak was going to resign at once. The misguided celebration eventually subsided.
Amnesty International cited witnesses as saying they saw trucks full of Mubarak supporters leaving Mahalla, an industrial city in the Nile delta, on Wednesday. It was unclear whether they were headed to the showdown in Cairo.
Protesters said they detained two-dozen low-ranking police officials who were involved in Wednesday's attacks, seizing their IDs and business cards. It was unclear, though, whether the men joined the fighting of their own accord or were instructed to do so.
Reports say cars made all-night deliveries of gasoline to pro-Mubarak fighters, hence their deep supply of firebombs. The well-stocked fighters also brought in boxes of koshari, a cheap local meal of rice, lentils and pasta.
Hala Mustafa, a senior member of the ruling party and a reform advocate, said she believed pro-Mubarak combatants were bankrolled by businessmen with government ties. A deep culture of official corruption has helped fuel the anger that propelled many Egyptians into the streets in protest.
Organizers of the pro-government crowds, she speculated, sought political legitimacy for the street action, even though it degenerated into deadly riots and systematic attacks on journalists covering the mayhem.
"They took advantage from the kind of sympathy that was created after the last speech of the president, to use it as a cover," she said.
Mubarak's televised declaration that he would not run for office again after his term ends in September resonated in some quarters. At a peaceful rally of supporters in Cairo's Mustafa Mahmoud Square, a large banner read: "Your speech made us cry, Mr. President."