Delayed police responses and an illegal street obstruction were contributing factors to the weekend's crowd crush in Seoul, officials said on Tuesday.
At least 154 people were killed, and dozens were seriously injured in the South Korea capital's Itaewon neighborhood as they celebrated Halloween on Saturday night.
The death count could further rise as many of those injured remain in critical condition, the country's Ministry of the Interior and Safety said.
Those killed or wounded were mainly teenagers and individuals in their 20s, according to Choi Seong-beom, chief of Seoul's Yongsan fire department.
Government investigators have scrambled to explain the night's logistical failures, such as insufficient police reactions and obstructive terraces, which escalated the fatality of the crush.
The first person called for emergency rescue at the site at 6:34 p.m., four hours before the crowd crush, the National Police Agency said. Firefighters arrived after 11 p.m., they said.
In total, witnesses made 11 emergency calls throughout the night, and police dispatched officers to the site four times, the agency said. The officers presumably did not realize the urgency of the crowd, according to local reports.
The National Police Agency is investigating its protocol, seeking to uncover why the rescue squad did not arrive earlier and why the force's control of the crowd was "inadequate," per the wording of its police chief.
In addition to the lack of police dispatched, authorities said they were looking into two makeshift terraces on each side of the back street of the Hamilton Hotel building. The terraces were illegal and caused the crowd's bottleneck pile-up, officials said.
Alley streets must be four meters wide, according to law, but the hotel's terraces shrunk the alley's width to three meters, just under 10 feet. Authorities in the ward office of Yongsan fined the Hamilton Hotel for the same violation last year, officials said.
The national police chief, Seoul's mayor and the prime minister all had separate press meetings on Tuesday, Nov. 1. Each apologized for their inability in preventing this tragedy, vowing to prioritize public safety.
ABC News' Joohee Cho and Hakyung Kate Lee contributed to this report.