Searches generally require probable cause, consent, or a search warrant. There are exceptions, and lots of them, for vehicles. If the items were in plain view, or if there was reasonable articulable suspicion that a crime was occuring or about to occur, or in the event the car were stopped, the area in immediate control of the passengers could be searched, or if the car were impounded it would be searched and inventoried.
So, in short, the answer is possibly yes, possibly no.