The parents of murdered schoolgirl Danielle Jones have visited the garages where police believe the teenager's body may have been hidden for the past 16 years.
The 15-year-old was last seen on Monday June 18 2001 at about 8am when she left her home in East Tilbury to catch the bus to school.
Her uncle Stuart Campbell was convicted of murder in December 2002 but her body has never been found.
Police drove Danielle's parents Linda and Tony to the cordoned-off garages between Goddard Road and Crammavill Street in Stifford Clays in Thurrock, where they stayed about 20 minutes.
Essex Police said they wanted to see the scene, in the heart of a residential area, and wanted to see what was going on.
In a statement the parents said: "We think of Danielle every day and we hope that this latest search may bring us answers about what happened to her 16 years ago."
Assistant Chief Constable Steve Worron, head of Kent and Essex Serious Crime Directorate, described the search as a "credible line of inquiry".
It was triggered after a member of the public told police in February this year of "unusual activity" at the site, he said.
A cordon was in place at the entrance to the alleyway where two uniformed police officers stood guard.
Mr Worron said this search could "conclude once and for all" if this is where the youngster's body has been buried, adding that "any search of this kind is significant".
Police said some non-specific information was received in 2001 relating to this garage area but these garages were not searched.
The disappearance of Danielle and subsequent murder investigation was one of the biggest cases that Essex Police have dealt with, involving more than 750 officers and staff.
More than 1,000 garages were included in the "huge number" of searches that were carried out in 2001 and 2002, according to Mr Worron.
He said: "I do know that in 2001 that garage block had not been searched by officers. This week we will conduct a search of that area to see if that is the location of where Danielle's body has been hidden since 2001.
"The reasons why that garage block was not searched aren't clear to me at the moment but we are working to understand that."
He could not say how much time would be needed to search the site because it will depend on how detectives "deconstruct and examine" the garages.
Mr Worron said: "We received information earlier this year that there had been unusual activity in the garage block and I am absolutely committed to conducting a thorough and professional search to see if we can bring the Jones family any closer to knowing what happened to Danielle 16 years ago."
Beyond the tall metal fencing, workmen were preparing the groundwork for excavation which is likely to start on Tuesday.
Police were nearby overseeing the preparation.
About four out of a dozen garage plots are still standing at the scene.
Detectives are believed to be focusing on one garage but this could change over the coming days.
It is also believed that some of the garages were still in use before this fresh search.