A kitchen fire inside a six-story apartment building sparked a two-alarm response in Norwalk Monday, sending heavy smoke through multiple floors and prompting firefighters to search occupied apartments.

Firefighters responded to 10 Monroe St. after an automatic fire alarm activation and reports of smoke in a third-floor hallway. Arriving crews found smoke coming from the building and declared a working fire.

Officials say firefighters located a kitchen fire inside a third-floor apartment. Command upgraded the response to a second alarm because of heavy smoke on the third and fourth floors and the need to search numerous occupied apartments.

A total of 31 Norwalk firefighters responded. All apartments were cleared, and no residents were injured. One firefighter was evaluated at the scene but was not taken to the hospital.

The fire was brought under control in about 30 minutes. The cause remains under investigation by the Norwalk Fire Marshal's Office.