LEWISTON — A nearby lightning strike sparked the fire that burned deep inside the Bates Mill early Wednesday morning, a fire investigator said later in the day.

A bolt of lightning hit something near the mill and ricocheted toward the top of the building, igniting wood under the roof of an old elevator shaft, Lewiston Fire Investigator Paul Ouellette said.

The fire was reported shortly before 11 p.m. Tuesday by a passer-by who thought he smelled smoke, a fire official said. When fire crews arrived in the area of Museum L-A, they found flames on the upper section of the old mill.

“I was walking in that area when I thought I smelled smoke,” said 37-year-old John Johnson, credited with reporting the blaze. “Then I could see a little bit of smoke, but I thought it might be just steam coming from the canals.”

Johnson then walked down Canal Street and saw that it was indeed smoke billowing from the roof of the old mill. He called 911 from a cell phone.

“When the firefighters got there, it wasn’t until they got up on the roof that they found the flames,” Johnson said.

Crews working from the alley behind the building, near DaVinci’s Eatery, encountered heat and smoke as they pressed into the building. A haze of smoke hung over the mill, visible from Lincoln Street on one side and from Canal Street on the other.

The area that burned houses Museum L-A, but the fire did not damage the museum or its contents, according to museum officials.

“(The firefighters) caught it early enough so that the sprinklers didn’t go off,” Museum L-A Executive Director Rachel Desgrosseilliers said. “Thank God, because the water damage would have been horrible for the artwork and the artifacts and the archive we have.”

Firefighters were able to contain the fire, which burned in the large tower attached to the Canal Street building, Bates Mill No. 1, preventing the fire from moving into the larger part of the mill.

The museum houses a historical archive of the Lewiston-Auburn community, documenting the mills and the people who worked in them. Desgrosseilliers said the museum is in the process of building an exhibit on the shoe-making industry.

The outpouring of concern and support from the community has been “unbelievable,” Desgrosseilliers said.

“Since early this morning, it’s been phone calls and e-mails from all over the community,” she said. Local businesspeople, members of the community, Bates College officials and representatives of Sen. Olympia Snowe, Sen. Susan Collins and Rep. Michael Michaud’s offices called to express concern for the museum’s welfare, she said.

“People have been calling off the hook,” said Susan Beane, the archivist and public relations coordinator for the museum.

As of 10 a.m. Wednesday, firefighting equipment had mostly moved out of the building.

“We’re not back to normal in the sense that it scared us, but as far as business goes, we’re back to normal,” Desgrosseilliers said.

“I’d like to thank the community and let them know that it means a lot to see how important their history is,” she said.

Museum L-A is in the process of planning a move to the Camden Yarns building off Oxford Street, but the timeline for that is still a few years away, Desgrosseilliers said.

“Last night made me wish it was going to be earlier,” she said.