A major operation involving 150 police officers from five forces has been carried out to stop an escalating feud which saw two teenagers' skulls being stolen from a grave.
The macabre act at Metal Bridge Cemetery, County Durham, was the latest in a series of shocking incidents involving two factions of the travelling community, police said.
The swoops on travellers' sites and homes in Doncaster, York, Middlesbrough, West Rainton near Durham, and Gateshead were aimed at getting more information about the feud.
Led by Durham Police, the operation led to a number of arrests, firearms being seized and vehicles towed away.
Dogs trained to find dead bodies were used to try to locate the stolen skulls, which belonged to brothers Levi George Price and Gareth Price, who both died aged 16, in 2001 and 2005 respectively.
The theft was carried out to antagonise a rival faction, police believe, and has sickened the majority of travellers.
At the site in West Rainton, police specialists were scouring the area around the neat bungalows for evidence.
It Gateshead, close to the International Stadium, around 30 officers were carrying out searches.
A silver Ford saloon was taken away on a police recovery vehicle, and sniffer dogs wagged their tails as they were sent into outbuildings.
A young girl riding her bike watched as the searches took place.
There was no sign of trouble at either site.
Detective Superintendent Adrian Green, leading the inquiry, urged whoever has the skulls to give themselves up.
"Your community is appalled at what you have done," he said.
He thanked travellers for coming forward with information since Monday, when news of the graveyard attack broke.
"It shows that the desecration of the grave and the theft of the skulls will not be tolerated by anybody."
He added: "We said it had gone too far. Police are taking positive action for which I hope the community are appreciative and feel reassured."
Chief Inspector Caroline Dawson works in Darlington where in recent weeks a home has been petrol-bombed and two others badly damaged after being rammed by lorries.
She said: "We must remember that these people who are involved in this crime are a small faction of the travelling community."
She said the majority "want to live a peaceful life".
Gareth Price was found hanging at Lancaster Farms Young Offenders Institution in 2005, the day before he was due to be sentenced for rape.
An inquest found he had been let down by a series of people in authority.
Levi George Price was found hanging in a shed in 2001. The coroner could not be sure the teenager intended to kill himself.
Police said on Wednesday that four people have been charged with conspiracy to commit GBH.