Do the police need a search warrant during a traffic stop to search a safe not attached to the car?

I believe they do need a warrant to check private property but if the safe is in the car and your entering a restricted area then they wont be needing a warrant.

ADDED: The questioner has neatly left out any explanation as to how and why this safe had anything to do with their vehicle. The police would have been derelict in their duty if they had not looked into the circumstances that they were apparently faced with. If the police had reasonable suspicion that this "un-attached" safe might be the "fruits of a crime" they will take action to either confirm their suspicion or set their suspicion to rest. After all . . . how many people drive around with "un-attached" safes in, or on, their car?