A method of determining a presence of items of interest within a cargo container is disclosed. The method includes obtaining information from an initial radiation scan of at least one of the cargo container and contents therein, identifying a target portion of the cargo container in response to the information obtained, transmitting a target radiation beam along the target portion of the cargo container, and detecting radiation received in response to the transmitting. The method further includes analyzing the detected radiation for a presence of items of interest, and in response to the analyzing, generating a first signal indicative of the presence of the items of interest, or generating a second signal indicative of an absence of the items of interest.