Exploration and mapping of the environment is a critical issue in mobile robotics. In this paper we present an approach to multi-robot exploration and mapping, which is based in a distributed bidding process, where the bids are calculated by each robot. When a robot reaches the target it makes a decision by itself, which involves every one of the team members without lost of time in a totally distributed behavior and without the necessity of a central module. Furthermore, if the selected goal is discovered for another robot, this robot send a stop signal and the process of bidding is restarted. The bid is computed such each robot will be assigned to a near unexplored frontier, while keeping the robots far from each other. The bid includes the distance of robot towards one of the frontiers, and the distances to the others robots toward their objectives plus the distance of these objectives toward the frontier. The numerical results demonstrate that our approach is efficient and fault tolerant.