Witnesses described smelling “burning rubber” and seeing “six-foot flames” at the entrance to Southgate Underground station in Enfield on Tuesday evening.
The man was held on suspicion of an act likely to cause an explosion to injure or damage property, and endangering safety on the railway.
London Ambulance Service said they treated three people at the scene for minor injuries while two others were taken to hospital.
The Met responded to the incident, which is now being investigated by British Transport Police.
The station has reopened with services running although some officers remain in the area to provide reassurance to passengers, British Transport Police said.
London Mayor Sadiq Khan said the explosion had been “confirmed as non-suspicious” and praised the emergency services “for a swift and professional response”.
The arrested man, who is from Enfield, has been released under investigation pending further enquiries.