Police hunting for a 35-year-old man wanted in connection with two "brutal" murders are involved in an "ongoing operation" on a housing estate.
Cleveland Police confirmed a number of officers were involved in the operation in the Pallister Park area of Middlesbrough as part of the huge effort to find James Allen.
More than 100 officers are now looking for Allen following the deaths of Colin Dunford in Middlesbrough on Monday and Julie Davison in Whitby, North Yorkshire, on Wednesday.
Allen is known to police and members of the public are urged not to approach him but to dial 999.
A Cleveland Police spokeswoman said no further details were available about the operation in the Pallister Park area.
Detectives described the killings as "two brutal murders in the victims' own homes".
Cleveland Police and North Yorkshire Police issued a joint appeal to find Allen after officers linked the two deaths.
Ms Davison, 50, who lived alone, was found dead by her sister at her rented flat in Church Square. She had suffered serious head injuries, police said.
North Yorkshire Police said they wanted a man with a dark-coloured mountain bike to come forward after he was seen near the flats at around 6.30am on Wednesday.
A post-mortem examination on Mr Dunford, 81, showed he had also suffered serious head injuries as a result of a significant assault.
He was found dead at his terrace house in Leven Street, Middlesbrough, on Monday after he failed to appear at his favourite club.
Locals said the dead man was a daily visitor to the Samuelsons Working Mans Club opposite his home.
It is believed that when Mr Dunford was not seen at the club, where he often ate his evening meal, members became worried and police were called.
Detectives said there was no sign of forced entry at the house.
Mr Dunford was last seen alive at around 5pm on Sunday.
Temporary Detective Chief Superintendent Gordon Lang, head of crime operations for Cleveland Police, said yesterday: "Anyone who can carry out such callous acts needs to be caught as a matter of urgency.
"We have over 100 officers working on the incident to trace Allen and we are focusing our efforts in Cleveland and in the Whitby area of North Yorkshire.
"Anyone who sees him or who knows where he is, we would ask them to contact 999 immediately."
Allen is described as 5ft 7in, with a bald head and tattoos on both arms.
Police stood guard outside a property in Lothian Road in Middlesbrough today as forensic officers in white boiler suits entered the property.
Neighbours said Allen was seen at the property at the weekend.
Adeel Baig said he last saw Allen at about 5pm or 6pm on Sunday evening as the suspect got into a taxi.
He said: "He was a normal bloke. Always polite. I thought he was trying to sort his life out."
He said he also saw him on Saturday with a baby who Allen said was his granddaughter.
"I was surprised. I thought it was his daughter. She was only about six months old.
"After that I saw him on Sunday as he walked towards a taxi. On the Sunday he had knocked on my door and asked to borrow some pots and pans."
Mr Baig said armed police flooded the street today.
"I had dropped my daughter off at school and arrived back at about 9.05. I was still in the car.
"Six or seven police vehicles arrived and officers got out with their weapons and ran to the house. They asked me to go to the bottom of the road. They were walking towards the house with guns."
Mr Baig said an elderly man in the house came out of the property with his hands up and was taken away by officers. He said the man had lived at the property for about 20 years.
Mohammed Salim Afsar, who lives opposite the raided house, said he saw Allen about four days ago.
"He was walking down the road quickly towards a taxi. He said he was a bricklayer and asked if I wanted any work doing.
"He said he was going to Scarborough. I recognised his photo and rang the police yesterday. I saw him, I recognised his picture."