Agent-based source seeking problem with switching formation and topology is addressed in this paper. This problem is relevant in, e.g., in hazardous gas leak in a chemical disaster, forest fires, nuclear disaster, etc. In the cooperative seek, agents develop a formation to effectively seek the source by communicating one to another via a communication topology. The source, or the seek target, is represented by a scalar field which describe, e.g., a temperature level, hazardous concentration of substances or vapor. Every agent has the information on its own position and the value of scalar field at any instance. The agents are identical modeled as single integrator. Consensus filter is used to synchronize the gradient value of each agent. Formation control is used to shape formation. In this paper three scenarios of switching formation are compared. These scenarios consist of 2, 3, and 4 formations respectively. The comparison is performed by computer simulation. In all scenarios, the formation of the agents can reach the sought source. The simulations show that the scenario with 2 formations is better than the scenario with 3 and 4 formations with respect to gradient connectivity of the cooperative multi-Agent.