Man police initially believed was stabbed Westminster Bridge actually suffered a cardiac arrest, the Metropolitan Police have confirmed.

Officers were called around 10:45 a.m. Sunday after a fight broke out on the Center Bridge London.

The Met Police attended the scene with the London Ambulance Service and London Air Ambulance and found a man suffering from cardiac arrest.

Law enforcement said initial reports suggested the man had been stabbed, but further investigations confirmed that was not the case.

The investigation continues and the man remains hospitalized in critical condition.

Three people were arrested on suspicion of attempted murder, and one person was arrested on suspicion of affray. Two of those arrested were taken to hospital with head injuries.

Police said they wanted to hear from anyone who was in the area at the time and may have witnessed the incident.

Anyone with information or images should contact police on 101, quoting CAD 2468/24NOV, or contact Crimestoppers anonymously on 0800 555 111.