We present a web-based method for mapping various relations between agents that have been involved in an emergency response operation. The method is based on combining a web-questionnaire with telephone interviews and it provides an efficient way of collecting large amount of information concerning the agents. By using the resulting network of agents, it is possible to perform various network analyses, such as identifying important agents and groups, analysing the correlation of certain relations between the agents, and studying the temporal development of the network. Furthermore, we illustrate the method by presenting results from an analysis of an emergency management operation concerning the release of 16,000 tons of sulphuric acid in the city of Helsingborg, Sweden. We conclude that the emergency management organisation included a significant amount of agents that were not part of any plans, such as boundary spanners and agents that were not part of any of the involved organisations but still played very important roles during the operation.