N.C. Gen. Stat. § 15A-251: Entry by force.

An officer may break and enter any premises or vehicle when necessary to the execution of the warrant if:

(1) The officer has previously announced his identity and purpose as required by G.S. 15A-249 and reasonably believes either that admittance is being denied or unreasonably delayed or that the premises or vehicle is unoccupied; or

(2) The officer has probable cause to believe that the giving of notice would endanger the life or safety of any person. (1973, c. 1286, s. 1.)