Does a search warrant need to be obtained to obtain a bottle from a defendant?

Defendant contends that, even if the officers did have probable cause to seize the bottles without a warrant, they violated his Fourth Amendment rights by conducting field tests to ascertain the contents of the bottles without first obtaining a search warrant. He argues that because this "search" exceeded the scope of the private search which had been conducted by the air cargo and airlines employees a warrant was required, citing Walter v. United States, supra, 447 U.S. at page 657, 100 S.Ct. at page 2401.