Police in Plymouth are linking a concrete block being thrown from the top of a multi-storey city centre car park with a later incident of affray.
The 40kg block was thrown from the top of the 80ft (24m) car park in Western Approach at 1700 BST on Wednesday.
At about 2100 BST a number of teenagers were arrested after a disorder incident outside a shop on Union Street.
All 11 of those arrested, who were aged between 15 and 18, were later released on bail, police said.
Higher police presence
When the concrete was thrown from the car park it narrowly missed two people, including a police community support officer (PCSO).
A 16-year-old boy was arrested on suspicion of attempted assault afterwards.
Those arrested in connection with the affray were also interviewed in connection with the concrete block incident.
Police said inquiries were continuing and a higher policing presence was in place around both areas.
The arrested teenagers were bailed to return to Charles Cross Police Station in September.