When Larry Mucciolo ran into his office early Monday morning to grab his gym bag, he thought the cigar in his hand was out.

Around 8 a.m. Northeastern Police and the Boston Fire Department responded to a one-alarm fire in Richards Hall, which Associate Director of Public Safety James Ferrier said probably started in the wastebasket of the senior vice president for administration and finance’s office.

“I actually had a cigar and it was out, unless it wasn’t and I dropped an ash, but I can’t be sure,” Mucciolo said. “I haven’t heard from anybody for sure what the cause might have been and I was speculating and being honest.”

The cause of the fire that closed Richards Hall for approximately 20 minutes and delayed morning classes, Ferrier said, is still under investigation.

Police and firefighters responded after a sprinkler in the office went off, activating the alarm.

“The automatic sprinkler system contained the fire and kept it from spreading and there was basically a charred wall and a melted waste basket,” Ferrier said.

He said the office and adjacent rooms also incurred some water damage from the sprinkler.

The three main doors to the building were left open and fans were placed in the doorways to rid Richards of the smell of burnt plastic.

Wendy Kamara, a Northeastern switchboard operator who normally comes in at 8:30 a.m., said she smelled the smoke and saw the fans when she arrived ready for work Monday morning.

“My co-worker comes in at 8 a.m. and he said the doors were locked when he got here,” Kamara said.

Though the fire was minor, the smell lingered throughout the building for some time.

“It didn’t really smell like a fire though,” said Holly Rapoza, a freshman finance major who works in the Office of Student Financial Services. “When I came in here, no one could pinpoint what it was. It was nauseating, it was so gross.”