The police investigation team probing the fatal Itaewon crowd crush has raided the Hamilton Hotel which stands on one side of the alley where more than 150 people lost their lives.

The Korean National Police Agency's special investigative headquarters sent 14 investigators to three locations on Wednesday, including the hotel and the residence of its chief executive, to obtain documents regarding hotel operations and licensing.

Earlier in the day, the headquarters launched a formal investigation against the chief executive on charges of unauthorized structural constructions around the hotel and the unauthorized use of roads for private purposes.

The headquarters is expected to verify how big of an effect the hotel's illegal structures had on the fatalities based on an analysis of seized data and an on-site inspection.