Detective Superintendent Wayne Fox, of North Yorkshire Police, said underwater search teams and forensic experts are likely to be in Sand Hutton Gravel Pits near York for “a number of days”, but did not reveal why they are working in that location.
The search began early today and officers have been seen in woodland areas and ponds which are used for fishing.
Ms Lawrence was last seen in March 2009, when she was 35-years-old, and detectives believe she was murdered, even though no body has been found.
Det Supt Fox said: Whilst I’m unable to disclose what brought us to this location, I would like to stress that the searches you will see in the coming days are just one of several active lines of enquiry which are being investigated and pursued by the North Yorkshire Police Major Investigation Team, and our efforts to establish what happened to Claudia and to identify any person responsible for causing her harm.
“I can confirm that Claudia’s family are aware of this activity taking place.”
Ms Lawrence’s friends and family became suspicious after she failed to turn up for her 6am shift at the University of York’s Goodricke College on Thursday, March 19 in 2009 and her father Peter Lawrence phoned the police the following day.
She was due to walk around three miles to work that morning, but she never arrived, and her mobile phone – a silver Samsung D900 – and a blue and grey Karrimor rucksack have never been found.
Police said she appeared to have left for work that morning, as the bed had been made and there were breakfast dishes in the sink.
She was last seen at around 3pm on Wednesday, March 18, when she was walking to her home on Heworth Road and she spoke to her parents on the phone later that evening. Both said she appeared to be in good spirits.
Mr Lawrence died earlier this year, at the age of 74, without finding out what happened to his daughter.
North Yorkshire Police said detectives have conducted two "extensive and exhaustive" investigations, taken thousands of statements, searched several scenes, trawled through thousands of hours of CCTV footage and even consulted experts from the FBI.
They have also arrested nine people, but no one has ever been charged.