Watch Rob Murphy's report
Police have been searching the holes, tunnels and caverns which line Bristol's ancient docks as part of a murder investigation.
Claire Holland was reported missing by her family on Thursday 14 June, 2012.
The 32-year-old was last seen at the Seamus O’Donnell’s pub in St Nicholas Street on Wednesday 6 June that year - just after the Queen's Jubilee weekend.
Now, almost 10 years later, Avon and Somerset Police are undertaking a "significant" operation in Bristol in connection with her disappearance.
Det Insp Darren Hannant from the Major Crime Investigation Team told ITV News: "We are not looking in the overtly public areas but there are certain parts of any city which remain untouched for many years.
"We've obviously looked at development and maps and changes in the layout over the years and there are some areas of the city which do remain untouched so we need to search some of those parts of the city."
In an interview with ITV News, the detective inspector said police believe Claire "may be dead" - but they do not know where her body is.
"Therefore we need to do everything we can to find her," he said.
The force has released CCTV footage of Claire on the day she disappeared as part of a renewed appeal for information from the public.
Who police want to hear from
Were you in the Seamus O’Donnell’s pub on the night Claire was last seen (Wednesday 6 June, 2012)? If you were and have not spoken to police, please do so now - they want to identify everyone who spoke to Claire on the day she disappeared.
Police are asking people to watch the CCTV clips and get in touch if they saw a woman matching Claire's description heading into Bristol city centre from the direction of St Nicholas Street after 11pm.
Claire is described as white, 5ft tall, of slim build, with shoulder-length brown hair, which was sometimes tied back in a ponytail.
If you saw her elsewhere in Bristol that evening, you should get in touch with police.
Police also want to speak to any friends or acquaintances of Claire.
"We need to know as much as we can about what Claire was doing or sharing with others in the days and weeks leading up to her going missing," a force spokesperson said.
They added: "Has someone told you information about this case which may have sounded unusual or suspicious? Has anyone confided in you about what may have happened to Claire? Now is the time to put aside any doubts you have had about making contact and help us find answers for the sake of Claire’s family and loved ones."
How to provide information to police
If you have information which could help the investigation, call police on 101 and give the call handler the reference number 5219172645.
Alternatively, you can call the independent charity Crimestoppers anonymously on 0800 555 111, or via their website www.crimestoppers-uk.org – they never ask for your name or trace your call.