This paper presents a new approach for multiple speaker DOA estimation using an array of microphones. The method relies on the fact that multiple independent speakers have a small overlap in the time-frequency domain, i.e. the individual signals are almost W-disjoint orthogonal. By introducing a time-frequency mask and by continuously track the set of time-frequency points corresponding to each individual speech signal, a single source DOA estimation algorithm is used to find the DOA for each separated signal. This approach does not limit the solution to cases where the number of sensors exceeds the number of sources. Real room recordings are used to evaluate the performance of the method where source movements are also included.