It may seem obvious, but building collapses of any magnitude represent a severe hazard to the firefighters and other emergency responders on scene.
Our natural inclination is to rush in and begin searching for victims.
Keep in mind, however, that all bets are off in a building where significant structural damage has occurred; if it failed once, the chance of further collapse is high.
Safely and effectively operating at a building collapse, like any other technical rescue incident, demands specialized training, equipment, and personnel. It's important to understand your department's capabilities and limitations in this area; if you can't address a technical rescue with available resources, know how to get a qualified team and call immediately for mutual aid.