If officers have a reason to believe that a container contains a 'dangerous instrumentality' such that opening the container is imperative for safety reasons a warrantless search is justified. See United States v. Chadwick, 433 U.S. 1, 15 n. 9, 97 S.Ct. 2476, 2985 n. 9, 53 L.Ed.2d 538 (1977).