Authorities at Heathrow Airport in London evacuated passengers from one of the terminals following suspicions of an incident involving hazardous materials. The London Fire Department reported that its personnel were called to Terminal 4 at the airport - one of the busiest in Europe - due to a "potential hazardous materials incident," emphasizing that the evacuation was carried out as a precautionary measure. The airport announced that all other terminals continue to operate but urged passengers not to come to Terminal 4.