A police officer was left with a broken wrist after being hit by a car as two suspected gunmen tried to flee cops.
Police were initially called after reports of a firearms incident on Stanhope Road, South Shields, late on Friday night.
The men were reported to have threatened a motorist and stolen money he had withdrawn from a cash machine at a Post Office.
As the driver tried to get away, his car overturned.
Officers later tried to stop a car on Sulgrave Road, Washington, where an officer was knocked over as police carried out their probe into the incident.
Two men have since been arrested in connection with it.
A Northumbria Police spokesman said: "Just before 11pm on Friday, September 22, police received a report that two men were seen with what is believed to be a firearm in South Shields.
"The men were seen opposite the Post Office on Stanhope Road.
"Two men were reported to have approached a car and threatened the driver inside.
"They proceeded to break the window with a crow bar and demanded a 34-year-old man's money that he had withdrawn from a nearby cash machine.
"The male driver attempted to drive away but in doing so his car overturned.
"The offenders went on to steal cash from the car before leaving the scene.
"A few hours later, at 5.13am on Saturday, September 23, officers were carrying out search inquiries for the two men in the offending vehicle.
"They attempted to stop a car on Sulgrave Road, Washington, but as an officer approached the car drove off, colliding with the officer, who sustained a fracture to her wrist, which required hospital treatment."
Chief Inspector Mark Hall said: "We've launched a full investigation into this incident and as a result two men have now been arrested.
"We're appealing for information from the public and anyone who saw the initial incident on Stanhope Road or the offending vehicle the following day is encouraged to get in touch."
Anyone who saw anything suspicious is urged to contact police on 101 or call Crimestoppers on 0800 555 111.