London Ambulance Service (LAS) sent a “hazardous area” response team to the airport on Thursday evening.
Five people who had been on board flight BA867 from Budapest were looked over by paramedics, LAS said in statement.
BA said the pilot had requested a priority landing after experiencing a “technical issue”.
Passengers on the flight said were put in “isolation” by emergency services after the plane landed at about 7pm, MyLondon reported.
Geraldine Fusciardi, who was one of the passengers detained, told the news website: "We were locked in the room for about 40 minutes.
“One woman collapsed in distress just as they were letting us out. No apology.
"Five minutes after they told us it was a major incident and physically prevented people from leaving the room - including some distressed women who needed the toilet - they released us all with some vague comments about engineering issue on plane."
A London Ambulance Service 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 (HART) to the scene.
“We assessed five people at the scene but did not take anyone to hospital.”
BA apologised to the passengers on board and said they were looked after by staff following the landing.
A BA spokesperson 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."
The Standard has approached BA and Heathrow for further comment.