Two Janesville residents are recovering from injuries after an explosion at a duplex Monday night.

Janesville Fire Battalion Chief Ron Bomkamp said someone lit a cigarette near a natural gas leak in the 800 block of Hawthorne Avenue.

One resident suffered serious injuries and a dog was taken to an emergency veterinarian hospital.

The duplex suffered heavy damage, with one unit declared a total loss.

A resident told firefighters that a water heater had smelled like natural gas for several days prior to the explosion.

Neighbors in the area reported a loud boom and feeling their houses shake.

The Rock County 911 Communications Center received a call for the explosion at 9:15 p.m., and the Janesville police and fire departments and Alliant Energy responded.