Five men have been arrested on suspicion of murdering a man who has not been since for a month.
Michael Wheeler, 37, from Yeovil, was last seen on August 24 and has not been in contact with friends or family.
His car was found in the Somerset town last week, according to Avon and Somerset Police.
The force said Mr Wheeler has also missed several appointments.
According to Avon and Somerset Police, the five men are in police custody and are in their late teens and 30s.
A sixth man who was arrested last week is on bail, the force said.
Det Ch Insp Lorett Spierenburg said: “We have been keeping an open mind over what has happened to Michael, who has now not been seen for a month, but we can confirm this is being treated as a murder inquiry.
“Arrests were made last week to enable us to question several individuals while under caution to understand if they knew anything that could help us locate Michael.”
She added detectives will be questioning all five men as part of ongoing efforts to establish what has happened and whether any criminal offences have been committed.
DCI Spierenburg said Mr Wheeler’s family is being supported by specially-trained officers.