SALEM, Ore. -- The Salem Fire Department says heavy equipment will remove portions of a collapsed roof Wednesday to help investigators find the cause of a New Year's Eve fire that damaged five businesses in a strip mall.
Federal investigators are looking into the three-alarm fire burned into Tuesday morning at Academy Square, with flames shooting through the roof in places.
Fire crews had to return to the scene overnight Tuesday after flames flared back up.
The department says the fire damaged a tax accountant's office, meat market, nail shop, game shop and paint store.
Workers left the meat market just hours before the fire started.
Investigators from the Bureau of Alcohol, Tobacco and Firearms (ATF) arrived Wednesday.
Investigators are interested in a video of the fire posted online that includes a conversation that mentions firecrackers, but the authenticity of the video has not been confirmed.
Justin Hiebert said he recognized voices from that video, and saw two men who appeared to be recording video near the fire.
"We were standing right here, and these two individuals were over here," said Hiebert. "And they were standing here with their cell phone and they were taking pictures and recording."
Brittany Green saw the posted video and said she knows whose Facebook page it was on. She believes it's essentially a confession.
"Why would you say 'I didnt mean for any of this to happen' and pretty much admit to throwing a firework if you didn't do it?" She said. "Why would you say 'oh, I didn't mean for this to happen. I just threw a firework as a harmless joke' and not do it? It doesn't make sense."
The video has since been taken down.
No one was injured in the fire.
Crews hope to move heavy equipment into the building Thursday to begin searching for what caused the fire.
The Associated Press contributed to this story.