Around 20 people were injured on Monday after a man sprayed an unidentified substance inside a luxury shopping center in Tokyo’s Ginza district.

Police said the incident occurred near a vending machine on the building’s ground floor, while ambulances and fire trucks rushed to the scene, and surrounding streets were closed.

Footage showed several injured individuals being transported to ambulances, while Japanese broadcaster NHK reported that the injuries appeared to be minor.

Authorities have launched an investigation to determine the nature of the substance and the circumstances surrounding the incident.