Tuesday marks one month since the deadly Halloween crowd crush in the South Korean capital of Seoul.

The incident in the capital's Itaewon district on October 29 left 158 people dead, including two Japanese citizens. Another 196 people were injured.

An investigation by a special police team is underway into officials who are suspected of professional negligence resulting in death and injury.

Investigators pointed out a lack of plans to ensure safety on the day of the incident. They also said authorities had been slow to respond to calls from people on the scene.

Yonhap News Agency said the investigation team is expected to finish questioning the former head of the police station overseeing the Itaewon district and other top officials this week. Police may seek arrest warrants for some of them.

A separate investigation is expected to open in parliament next month, in a bid to get to the bottom of the tragedy and to prevent a similar incident in the future.

The main opposition Democratic Party is increasing pressure on President Yoon Suk-yeol's administration, demanding that Interior and Safety Minister Lee Sang-min be sacked, citing his poor handling of the incident.