Given a map of a polygon-shaped search area with obstacles and a group of mobile networked observers equipped with radiation dose counters (such as the Geiger-Muller counter), the data fusion problem is twofold: (1) to establish if any radioactive point sources are present in the area; (2) if present, to determine their number and their parameters (locations and intensities of radiation). The detection/estimation part of the problem is solved in the Bayesian framework using a particle filter. The control of multiple observers during the search is carried out by maximization of the information gain measured by the Renyi divergence.