Merseyside Police stated that the two response vehicles collided in Tuebrook after responding on blue lights to two separate emergency calls.
The North West Ambulance Service transported two male and two female officers to the hospital.
Two of the officers have been released from the hospital.
It is believed that no other vehicles were involved in the crash.
Merseyside Police Serious Collision Investigation Unit Sergeant Steve Smith stated:
We are investigating the collision, and CCTV and witness inquiries are ongoing.
I would like to reach out to anyone who was driving along West Derby Road in the early hours of this morning and witnessed the collision or can assist us with our investigation.
Road closures will remain in place today while we conduct our investigations, and I would like to thank the public for their patience as we deal with this incident.
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