LITTLETON, Colo. >> Authorities reviewed security video Thursday from a Colorado mall where the discovery of a pipe bomb and two propane tanks after a fire raised concerns about a possible link to the Columbine High School attack.

The blaze coincided with the 12th anniversary of the deadly shooting two miles away.

"We’re concerned about the date, the time, things of that nature, but we don’t have anything solid that would indicate any link at all other than, certainly, circumstances," Jefferson County Sheriff Ted Mink said.

No arrests have been made, but dozens of law enforcement agents were scouring the video and following other leads to identify a man seen entering the mall through a side door not normally used by the public.

The mall reopened Thursday.

Mink said the community shouldn’t feel threatened, hinting that progress was being made in the investigation.

"It isn’t a situation where we don’t have a good handle of the direction where we’re going," he said, declining to elaborate.

The propane tanks found at Southwest Plaza Mall were discovered in a hallway of the food court after the fire was reported around 11:50 a.m. Wednesday.

The Columbine shootings started at 11:12 a.m. and ended 24 minutes later on April 20, 1999. Unexploded pipe bombs and a propane tank with explosives attached were found in the school cafeteria after the shooting.

Through the years, students across the country have been accused of threats and incidents modeled after Columbine, where 12 students and one teacher were killed.

"The kind of crime like Columbine will motivate a certain segment of the population to attempt the same type of crime," said Brian Rohrbough, whose son Daniel was killed at Columbine. "Whether they’re doing it because they’re purely evil or in addition to being evil, they just want attention, I don’t know."

Investigators were trying to find the man seen entering a stairwell through the side door and on an escalator in the mall.

Authorities also were investigating the cause of the fire, including whether it was sparked by the failed detonation of the bomb, West Metro Fire Rescue spokeswoman Cindy Matthews said.

Denver FBI special agent in charge Jim Yacone said investigators intended to interview several other witnesses.

Despite authorities’ assurances about safety, the community seemed uneasy.

Students at an elementary school in Littleton were evacuated to another school Thursday after a man entered the building to use a restroom.

Schools also were locked down following the fire at the mall on Wednesday and alerts were sent to malls in the Denver area.

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Associated Press writer Sheila V Kumar contributed to this report from Denver.