As the country began a week of mourning, the death toll climbed to 154. Another 149 people were injured, 33 of them in serious condition. At least 26 citizens from 14 countries were among the dead.
South Korean President Yoon Suk-yeol called for a thorough investigation, and authorities said they were focused on reconstructing the lead-up to the surge and looking at whether anyone may have been responsible for triggering the crush.
"We are analysing CCTVs to find out the exact cause of the accident," Police chief investigator Nam Gu-jun told reporters.
"We will continue questioning more witnesses, including nearby shop employees," he said.
Tens of thousands of revellers - many in their teens and twenties and dressed in costume - had crowded into narrow streets and alleyways of the popular Itaewon district on Saturday for the first virtually unrestricted Halloween festivities in three years.
Chaos erupted when people poured into one particularly narrow and sloping alley, even after it was already packed, witnesses said.
Prime Minister Han Duck-soo, who steers a task force team handling the accident, said the identification of the victims was nearly complete and funeral preparations could move ahead, promising support for the bereaved families.
Makeshift altar
On Monday, people laid white chrysanthemums, drinks and candles at a small makeshift altar off an exit of the Itaewon subway station.
Jung Si-hoon, a retiree, placed an old wooden cross at the altar, saying nothing could be done to bring back all the young people who had died.
"Those poor people, all at similar ages to my grandchildren... What more should we say? We should pray for them and wish they rest in peace," he said.
On Monday afternoon, dozens of crime scene investigators and forensics officers descended onto the trash-strewn alleys which were eerily quiet with many shops and cafes closed.
One agent with the National Forensic Service team, in white overalls and a black ribbon of mourning pinned to his chest, operated a Leica 3D scanner, he said, "to capture the scene."
Yoon paid his respects to victims at a memorial altar near the Seoul city hall on Monday, a day after visiting the crush scene and designating Itaewon a disaster zone.
He also met Han and other officials handling the accident, calling for a thorough investigation, support for victims and their families and safety measures over unorganized large gatherings.
Yoon said he felt "indescribable sadness and responsibility as the president in charge of the life and safety of the people," and it was so tragic that many young people, in particular, lost their lives, his deputy spokesman said.
"Above all, it is important to thoroughly investigate the cause of the accident and transparently disclose its results," Yoon was quoted as telling the meeting.
"It is necessary to come up with a safety management system for preventing crowd accidents that can be applied to voluntary group events without an organizer like this one."
Schools, kindergartens and companies around the country scrapped planned Halloween events. K-pop concerts and government briefings were also canceled.
The crush came as Itaewon was just starting to thrive again after more than two years of Covid-19 restrictions. The disaster is the country's deadliest since a 2014 ferry sinking that killed 304 people, mainly high school students.
Han said there had been incidents of people propagating hate speech by blaming victims, as well as incidents involving the spreading of false information and the posting of disturbing scenes of the crush online. A National Police Agency official said they were investigating six related cases.