Two Lawrence families were displaced early Wednesday morning after a fire damaged a duplex near West Second Terrace and Michigan Street in northern Lawrence, fire officials said.

Division Chief Eve Tolefree, a Lawrence Douglas County Fire and Medical spokeswoman, said the fire at 1402 W. Second Terrace started accidentally after someone improperly discarded smoking material.

Two occupants of the duplex were treated for minor injuries, but no one was taken to the hospital, Tolefree said. No firefighters were injured.

Firefighters were called at 2 a.m. to the single-story duplex, and initial crews discovered that fire, which started outside, had spread inside and into an attic area. The fire was brought under control at 2:45 a.m.

Quick thinking by a neighborhood newspaper carrier helped alert residents to the blaze. Leslie O’Brien, 25, said she and her mother, Sandy O’Brien, were driving by as they delivered the Journal-World’s River City Pulse publication at 2 a.m. They noticed a mattress leaning against the house was on fire, so Leslie O’Brien ran up and rang the doorbell several times as her mother called 911.

The ringing woke up one of the residents inside who tried to put out the fire until police and firefighters arrived, she said.

“I just decided I needed to make sure everyone was safe, so I rang the door bell like crazy,” Leslie O’Brien said.

Tolefree said, and the blaze caused an estimated $20,000 in damage.

County records value the duplex at $150,800.

Kristy Wempe-Bellinger, health and safety director of the Douglas County chapter of the American Red Cross, said the agency was providing assistance for lodging and food for the two families.

The chapter was still assessing what other assistance was needed, she said.