Mr Thompson's work van was found in Bushey on 4 May
Police forensic experts have been examining a Hertfordshire flat as part of their search for a missing man.
Murray Thompson, 34, from St Peter's Street in St Albans, was last seen at home on 20 April.
The Bedfordshire and Hertfordshire Major Crime Unit have been investigating his disappearance. They found his work van in Bushey on 4 May.
Police said a flat in Watford, where it is believed Mr Thompson had spent time, had been forensically examined.
Mr Thompson is described as white, 5ft 10in (1.7m) tall with straight brown hair.