A structure fire at an apartment in Boulder on Friday evening left none injured and several residents displaced, according to a news release from the city on Saturday.

About 5:30 p.m., Boulder Fire-Rescue firefighters were sent to a fire in a first-floor apartment in the 4900 block of Thunderbird Drive. Firefighters extinguished the flames and contained them to the single unit.

The fire displaced the resident of the unit as well as neighbors whose apartments were affected by the smoke. All have found alternate housing.

The apartment’s sprinkler system was activated when the fire broke out, helping firefighters quickly put out the flames, according to the release. Based on an initial investigation, the cause is possibly a front window heating or cooling unit. An official cause will be stated once the investigation is complete, the release said.