Cleveland Police said officers had received reports before the crash on Saturday of two cars being driven dangerously, including a vehicle that was seen ramming properties in the Middlesbrough area.
Both vehicles had been operating with cloned number plates to avoid detection, police said.
One of the vehicles drove the wrong way down a major road and crashed into a police armed response car, killing all five occupants and two police officers.
Four of the five occupants of the vehicle that crashed had previous convictions, police said.
Police said inquiries over the weekend had resulted in the arrests of nine men and three women, aged between 19 and 61, across the Teesside area.
The suspects were arrested on suspicion of offences ranging from possession of a firearm to participating in the activities of an organised crime group, police said.
"This has been a fast-moving and complex investigation, with significant links to serious and organised criminal activity," Assistant Chief Constable Wayne Fox said in a statement.
Police added there was currently no evidence that the events leading up to the crash had been filmed to appear on short-form video platform TikTok, after recent concerns in neighbouring Ireland about motorists driving the wrong way on roads for social media attention.
