Transcripts of 11 calls received by South Korean police on Saturday night show the first warning of a possible deadly surge was made at 6.34pm by a member of the public who said: “Looks like you can get crushed to death.”
National police commissioner general Yoon Hee-keun on Tuesday acknowledged crowd control at the scene in Itaewon was "inadequate", noting that police had received multiple reports warning of possible risks on the night of the disaster.
The interior minister and the city mayor have also apologised, while safety experts said proper crowd and traffic control by the authorities could have prevented, or at least reduced, the surge of partygoers.
The emergency call transcripts, released to the media, give a chilling prediction of how the tragedy would unfold.
"Looks like you can get crushed to death with people keep coming up here while there's no room for people to go down," a person said in the first call. "I barely managed to leave but there are too many people, looks like you should come and control."
The crush on Saturday night killed 156 people, many in their teens and twenties, and injured another 151 as revellers flooded the narrow alleyways of the popular Itaewon district to mark the first virtually unrestricted Halloween festivities in three years.
South Korea’s 112 emergency number received 10 more similar calls in the hours before the chaos was known to have turned fatal — and released all those transcripts on Tuesday.
Roughly 100,000 people were estimated to be in Itaewon on Saturday, an area known for its hills and narrow alleys. There were 137 police officers there at the time, the authorities have said.
"People are falling down on the streets, looks like there could be an accident, it looks very dangerous," one caller said at 8.33pm, according to the transcript.
The last call released by the police came at 10.11pm, minutes before people packed into one particularly narrow and sloping alley began to fall over each other shortly before 10:30pm.
"[People] will get crushed to death here. It's chaotic," the transcript of that call says, noting that screams were heard over the phone.
The transcripts appear to confirm the accounts of eyewitnesses who said they saw some police directing traffic on the main road but few or no officers in the crowded pedestrian alleyways and side streets.
Police went to the scene for four out of the 11 calls, a police official told reporters. It was not immediately clear why they did not deploy officers on the other calls or what safety measures they took after arriving.
"Those things are all under inspection now, so it's difficult for me to answer at this point," a National Police Agency official said when asked about this by news agency Reuters.
The official did not elaborate on the contents of the transcripts.
"The police will speedily and rigorously conduct intensive inspections and investigation on all aspects without exception to explain the truth of this accident," Mr Yoon told a news conference on Tuesday.
As police began investigating how so many people were killed, Prime Minister Han Duck-soo said the probe would also cover whether government agencies' on-site responses were appropriate.
President Yoon Suk-yeol has declared a week of national mourning and called for better safety measures to manage crowds, even when there is no central organising entity.
The festivities in Itaewon did not have a central organiser, which meant government authorities were not required to establish or enforce safety protocols.
The disaster is the country's deadliest since a 2014 ferry sinking that killed 304 people, mainly secondary school students.