Three police officers and two paramedics were rushed to the hospital after being hit by a van while responding to an accident.
Emergency services were called to the A130 in Essex after a single-car collision at around 12.15am this morning.
The force said that while the paramedics and off-duty officers stopped to help a Nissan X-Trail, there was a second collision involving a white Ford Transit van.
Two paramedics and three officers were taken to hospital following the collision. One of the officers and one of the paramedics suffered serious injuries and remain in hospital.
Three people have since been arrested.
A 23-year-old man from Canvey has been arrested on suspicion of causing serious injury by dangerous driving, theft of a motor vehicle and driving while unfit through drink or drugs.
A 29-year-old man from Westcliff has been arrested on suspicion of causing serious injury by dangerous driving, theft of a motor vehicle, possession of a Class B or Class C drug and being in charge of a vehicle while unfit through drink or drugs.
A 39-year-old man from Canvey has been arrested on suspicion of causing serious injury by dangerous driving and driving while unfit through drink or drugs.
The A130 was closed for a number of hours between Sadlers Farm roundabout and the A1245, with the road reopening shortly before 11am.
Three vehicles, including an ambulance, have been seen being taken away from the scene.
Chief Superintendent Morgan Cronin said: 'The thoughts of everyone at Essex Police are with the emergency workers injured while responding to this incident - both they and their families are being provided with support from the force.
'I'd stress this investigation is now active and we would encourage members of the public not to speculate, and to let our teams establish the facts of both these incidents.
'Those arrested remain in custody and we are working through inquiries at pace.
'If the public have any information - or crucially dashcam footage of the vehicles involved - that they believe will assist our investigation, please get in touch.'