Police investigating the disappearance of Sarah Everard are searching a home and woodland in Kent following the arrest of a serving Met officer.
The 33-year-old was last seen in Clapham, south London, on 3 March.
The policeman and a woman were held at a house in Kent on Tuesday. Searches are being carried out at a building in Deal as well as on land near Ashford.
The Met said it was “shocking and deeply disturbing” that the arrested man was a serving officer.
Ms Everard’s family have been kept updated, the force added.
A tent has been erected outside a house in Deal and a car was earlier seen being taken away from the property.
Officers have also been carrying out searches on land near to Great Chart Golf and Leisure in Ashford.
In a statement, the Met Police said the man and the woman had both been taken into custody at a London police station.
Assistant Commissioner Nick Ephgrave said the arrests were “a serious and significant development”.
“We will continue to work with all speed on this investigation but the fact that the arrested man is a serving Metropolitan Police officer is both shocking and deeply disturbing.”
During a later statement, he added the officer “was not on duty at the time” when Ms Everard went missing and would only confirm he had been arrested “in connection” with her disappearance.
He also would not say if the officer was known to the 33-year-old.
When asked by reporters if police believed she was still alive, Mr Ephgrave replied: “We are searching as hard as we can to find Sarah, so we really hope that is the case.
“As a father myself of four young women I can only imagine the anguish that Sarah’s family are feeling at this very very difficult time.”
The arrested woman has been held on suspicion of assisting an offender, the force has confirmed.
On Tuesday officers searching for Ms Everard had put up a cordon outside a block of flats in Clapham near to where she was last seen on Poynders Road and sniffer dogs have been used to search the nearby Oaklands Estate and gardens.
Officers were also seen searching drains along the street where Ms Everard was last seen.
The Met said officers had visited 750 homes in the area as part of the investigation and the force had received more than 120 phone calls from the public.
Friends and relatives have issued appeals on social media to help find the marketing manager, who vanished on her walk home to Brixton after leaving a friend’s flat in Leathwaite Road in Clapham Junction at about 21:00 GMT.
Her family has said it is out of character for her to disappear.
Ms Everard, who is originally from York and attended Durham University, was last seen wearing a green rain jacket, navy blue trousers with a white diamond pattern, and turquoise and orange trainers. She is thought to have been wearing green earphones and a white beanie hat.
She is believed to have walked through Clapham Common towards her home – a journey that should have taken her about 50 minutes.