Detectives investigating the disappearance and murder of a man from London have been searching woods in Buckinghamshire.
Mohammed Shah has not been since since failing to return to his home in Hounslow on 7 May.
In June the 27-year-old’s car was found with ballistic damage and a murder investigation was launched.
Det Ch Insp Noel McHugh confirmed an area in Hedgerley Lane near Gerrards Cross is being searched.
He warned the search could take “considerable time”.
“A substantial reward of £20,000 remains on offer for information that leads to the arrest and conviction of those involved,” Det Ch Insp McHugh said.
Seven men, aged between 19 and 25, have all been arrested and released under investigation in connection with Mr Shah’s suspected death.
Speaking in June when the murder investigation was launched, Det Ch Insp McHugh said Mr Shah might have been involved in criminal activity.
“When you remove the possibility that he’s taken his own life, left the area voluntarily, or had an accident, there is a strong suggestion that there has been third-party involvement in him going missing,” he said.
“I believe that Mohammed has got out of his depth in some kind of criminal activity.
“At this time there is a wall of silence and people are in the know. We need those people to come forward and tell us what they know.”