Police are searching a lake for a missing 32-year-old woman who they suspect has been murdered.
Natalie Jenkins, from Thornaby, Teesside, vanished in Middlesbrough in December and her body has never been found.
Two men, aged 40 and 66, were arrested on suspicion of murder earlier this week, while a 65-year-old woman was held on suspicion of perverting the course of justice. They have all since been bailed.
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Specialist officers from Cleveland Police are now searching the 30 hectares of Albert Park, with an underwater team checking its lake and waterways for any sign of Ms Jenkins.
The force said it was focusing its hunt on the inside of the park after information had come to light, and that it was expected to last several days.
Last month, detectives released CCTV footage of Ms Jenkins walking towards the park at 11.38pm on 10 December – the day she was last seen.
Police have offered a £10,000 reward for information that leads to a conviction of the person or persons responsible for her murder.
Senior investigating officer detective chief inspector Mark Dimelow said: “Our searches in Albert Park will take several days and will involve teams of officers led by trained search advisers.
“The area around the park has always been a significant location to our investigation and information has led us to focus on the inside of the park.
“I can’t divulge what this information is for operational reasons but we are still appealing for people to come forward to tell us what they know.
“We’re providing support to Natalie’s family and are keeping them updated with what is happening with the investigation.”
Detectives have previously said Ms Jenkins was particularly vulnerable because she was a drug user and sex worker.
She is described as white, 5ft 5in and slim, with fair skin and straight brown hair.
She has hazel eyes and a missing front tooth, and has tattoos saying “Swanny” on her neck and “Swann” on her wrist.
Additional reporting by Press Association.