The demand for content-based management and real-time manipulation of audio data is constantly increasing. This paper presents a method to identify temporal regions, in a segment of co-channel speech, as being either single-speaker or multi- speaker speech. The state of the art approach for this purpose is the kurtosis. In this paper, a set of complementary time- domain and frequency-domain features is studied. The employed classification scheme is the one-class SVM classifier. A recognition rate of 94.75 % is reached. The set of features providing the best performance is determined.