An 86-year-old man has been arrested on suspicion of murder after human remains were discovered in a septic tank.
They are thought to belong to Brenda Venables, a woman who disappeared in 1982, detectives said, after they were found in the Worcestershire village of Kempsey.
The 48-year-old was reported missing by her husband David but has not been seen since.
After discovering the human remains during a routine emptying of a septic tank earlier this month, West Mercia Police launched a murder investigation.
Investigators are now searching the bungalow where Mr Venables, 86, now lives in the village.
Three marked cars including a police van and two unmarked cars were outside the detached property in the usually quiet cul-de-sac, where a red estate car could be seen parked on the driveway.
Officers wearing gloves could also be seen inside the property. Police would not be drawn on activity at the scene other than to say it was “a line of investigation”.
The force said in a statement that an 86-year-old man was “helping officers with their enquiries”.
A spokesperson said detectives were still awaiting DNA results but “the general circumstances lead us to believe” that the remains are likely to be those of Ms Venables.
Mr Venables’ neighbours said he kept to himself and always had the blinds drawn at the front of his home.
“That’s normal,” said a female resident, who declined to be named. “We don’t see him, really. He gets out of his bungalow and into his car and then comes back.”
She added that police had not been around since the arrest but did speak to neighbours after the remains were discovered earlier this month.
“These things don’t happen too often, luckily,” she added. “It’s quite astounding. To actually find somebody in a cesspit.”
Another man, who lives a few doors down, said: “We’ve said hello to him, but we don’t know him. It’s a friendly, sleepy neighbourhood.”
In May 1982, Mr Venables told the Worcester News: “I just woke up to find that she had gone. She has never done anything like this before and I haven’t the faintest idea what has happened to her.”
Police said the formal identification process was likely to take a few weeks.
Additional reporting by Press Association
