A student has found more than 50 street signs in South and West Oxfordshire that have been damaged by gunfire.
Danae Prokopiou, of Cranfield University, in Shrivenham, is researching the types of weapons that caused the damage.
The study is part of Ms Prokopiou's Masters in Forensic Engineering.
It follows a BBC Oxford investigation that found six separate signs in West Oxfordshire which had been vandalised.
Forensics experts from Cranfield University said they are working with Thames Valley Police to assess the damage.
Professor Derek Allsop, Ms Prokopiou's lecturer, said he had inspected the signs and confirmed firearms had been used.
He added: "The weapons and the ammunitions that have been used are in nearly every case very, very lethal.
"They are hard targets. The projectiles can be ricocheted in any direction. It's a very dangerous thing that they're doing."
Thames Valley Police said in February it had not heard of such incidents before, but urged people with information to contact the force.