PASSENGERS were caught in a "brawl" at Heathrow Airport after they were evacuated off a British Airways flight which sparked security alerts amid fears of a "mid-air chemical incident".The BA876 flight from Budapest landed shortly after 7pm on Thursday evening and passengers were reportedly taken from the plane and "detained" at Heathrow Gate 26. A hazardous response team (HART) was sent to the scene by the London Ambulance Service, the police and fire brigade also attended. One passenger claimed on social media people were being detained without being told the details of the situation.The social media user also claimed a fight broke out between passengers and ground staff.Mark Weston shared on Twitter his wife and son were on the inbound flight.He added how they were "physically checked" but no information was provided about the incident.A London Ambulance spokesperson said: "We were called at 6:55pm today to reports of an incident at Heathrow Airport, Hounslow."We dispatched an ambulance crew, two incident response officers and our hazardous area response team to the scene."We assessed five people at the scene but did not take anyone to hospital."A British Airways spokesman said: "Our aircraft requested a priority landing as a precaution after experiencing a minor technical issue."Our teams looked after our customers and helped get them on their way as soon as possible. We are sorry to our customers for the delay to their travel plans."