An additional two individuals are now in custody related to a robbery at Heathrow Airport in which 21 people sustained injuries by a substance believed to be an irritant spray, according to law enforcement.
A man, 24, was arrested in Lambeth on suspicion of theft and assault and a woman, 23 was arrested for suspected conspiracy to commit robbery. Both individuals remain in custody, the force said.
The arrests come after an investigation into an assault at the multi-level parking garage at Heathrow's Terminal 3 on Sunday. Prior to the incident, two women were robbed of their luggage upon exiting a car park lift.
A three-year-old girl was among the those hurt during the incident. A total of five individuals were taken to the hospital for medical care and were later discharged.
Police arrested a 31-year-old man for suspected theft and assault near the scene. He was subsequently released under investigation as the investigation proceeds.
Police were alerted at about 8:10 in the morning GMT following reports of several people injured by a noxious substance believed to be pepper spray.
The assault - which authorities stated was isolated and not being treated as terrorism - caused train delays and the temporary shutdown of the Central Terminal Area tunnel and the T3 car park for a short time.
