A 34-year-old man was arrested on suspicion of possession of a controlled drug and theft from a motor vehicle in Yeovil today.
Police were alerted to a man acting suspiciously near cars parked in the Goldcroft and Highfield Road area at around 7.30am this morning.
Police say they have recovered a Navman S70 satellite navigation device with a number of local addresses on it.
They believe it to be stolen but so far no one has reported the theft of a sat-nav.
The arrested man remains in custody.
Car owners in the area are asked to check their vehicles and report any thefts to police.
Victims should contact PC John Greatbatch at Yeovil Police Station on 101.