A special investigation team from South Korea's National Police Agency raided more than 50 locations on Tuesday, including the office of the agency's head, in connection with the deadly Itaewon crowd crush in Seoul.

At least 156 people were crushed to death in the capital's Itaewon entertainment district on October 29. The victims included two Japanese and many other foreigners.

Local media say the special investigators conducted a sweeping search of police and administrative institutions that responded to the deadly accident. They seized documents and mobile phones to study what security measures were taken at that time.

The police had reportedly failed to prepare for a crowd surge, even though the risks had been pointed out beforehand.

Criticism is mounting in the country over top police officers' initial responses to the accident.

It has been reported that the National Police Agency's commissioner general failed to notice urgent calls immediately after the crush because he was at a campsite. He is said to have learned about the accident after President Yoon Suk-yeol was notified of it.

Although the period of national mourning ended on Saturday, many stores in Itaewon remain closed and fewer people are on the streets.