LINCOLN, Neb. (KLKN) — Lincoln Fire & Rescue revealed the cause of the massive fire at the Fairfield Inn & Suites on Monday.

LFR said an improperly disposed of cigarette sparked the blaze at 27th and Superior streets.

MJ Lierman, a LFR spokeswoman, said the cigarette lit the west side of the building and the flames worked up to the roof. Lierman said no one noticed the flames and smoke for several minutes.

Lierman said a passerby saw the flames around 6:50 p.m. on Monday, called 911 then went inside the hotel, alerted the front desk and an employee then pulled the fire alarm.

She said that allowed LFR time to evacuate the building. The roof collapsed along with the second and third floors once everyone was evacuated.

Smoke could be seen from miles away. By the time firefighters got to the scene, the top of the hotel was engulfed.

Several witnesses reported an explosion in the building. Lierman said that is called a “smoke explosion,” caused by the older insulation in the building.

LFR determined the building is a total loss.

Dozens of spectators watched from the sidelines. Many had been staying in the hotel, but they evacuated when they heard the fire alarms.

Several onlookers told Channel 8 they only had one focus: to get to safety.

Ryan Viets is from Minnesota. He is staying in Lincoln until Wednesday for work.

He recounts what it was like when the hotel alarm first went off.

“I knew I had to get out when I saw the smoke,” he said. “We couldn’t even get down the west side stairwell.”

LFR has been on the scene most of Tuesday monitoring hot spots.