Exeter murders: Three men in 80s had 'serious head injuries'
Three men in their 80s found dead had all sustained serious head injuries, police said.
Twin brothers Dick and Roger Carter, 84, were found dead at a house on Cowick Lane, Exeter, on Tuesday.
The body of 80-year-old Anthony Payne was discovered at a property in the city the day before.
A 27-year-old man has been arrested on suspicion of murder and remains in police custody. Detectives have until 22:00 GMT on Friday to question him.
Det Ch Insp Roy Linden, from Devon and Cornwall Police, said there was "no clear motive" and "no clear relationship" between the parties involved.
Police confirmed a gun was not involved in the murders, following reports of one being found at a property.
Supt Matt Lawler said officers had specifically visited nine addresses to check on the safety of elderly or vulnerable occupants, but there was no information to indicate a threat to any other person.
Officers have seized nearly 300 exhibits as part of the investigation and are pursuing more than 155 "priority" lines of inquiry, Det Ch Insp Linden said.
Supt Lawler added: "Following yesterday's media appeal, further important witnesses have come forward with highly relevant information."
Emergency services were first called to Bonhay Road at 15:00 on Monday where they discovered the body of Mr Payne.
At 13:00 on Tuesday, police found the Carter brothers dead about 1.5 miles (2.4km) away.
Police said the deaths were originally treated as two separate murder investigations but linked them because of the level of violence involved.
A police cordon is still in place at the Cowick Lane house and a small collection of floral tributes was added to overnight.
Dick and Roger Carter were born in September 1934, and were both directors of an agricultural company called Traycrop from the early 1990s until it was dissolved in 2004.
On Thursday, police were still at the house in Bonhay Road, which has a white crime scene tent around the front door.
Emil Sokolov, a 24-year-old student who leaves nearby, said he walked past the house every morning and evening but did not know the man who lived there.
"It's really sad. It's like having two worlds - you have the student area and with the local people, we don't really know that much about them, not in a bad way," he said.
"Students have their own thing and people have their own thing but when something like this happens the two worlds come back together."