Gary firefighters responded to a small fire Tuesday afternoon inside Dunbar-Pulaski Middle School.
The firefighters arrived at the now-defunct middle school at 2 p.m. and put out the fire within 20 minutes.
Gary Fire Department spokesman Mark Jones said some trash on the first floor caught fire, but declined to speculate whether it was arson.
The cause remains under investigation.
Dunbar-Pulaski Middle School is the highest-priced of 33 shuttered schools in Gary currently up for sale, valued at $5.85 million. It closed in 2015 because of poor performance.
Gary Mayor Karen Freeman-Wilson recently said the Gary Fire Department has responded to six arsons at shuttered schools at in the past 12 months, including two at Horace Mann High School and Ivanhoe Elementary, and one each at Lew Wallace and Washington Carver.