By Keith Coffman
GOLDEN, Colo. (Reuters) - Authorities asked for the public's help on Thursday in locating a gray-haired man caught on surveillance videos and sought in the investigation of a homemade bomb planted at a shopping mall near Columbine High School.
The FBI released a third photo taken from video footage on Wednesday of the unidentified man with a mustache and baseball cap, the latest one showing him at the top of an escalator at the Southwest Plaza Mall.
In all three pictures the man, wearing a dark jacket and striped shirt and described only as "a person of interest" by investigators, is seen carrying a plastic grocery bag.
Neither the FBI nor Jefferson County Sheriff's Office would say whether they considered him a suspect or why he was singled out for attention, only that they are eager to speak with him.
"There's an urgency to find the individual for obvious reasons, and we're using all the resources we have ... to run down this person of interest in those photographs," Jefferson County Sheriff Ted Mink said at a news conference in Golden.
The shopping mall, about a mile from Columbine, was evacuated on Wednesday after firefighters called to the complex for a small blaze in the food court discovered two propane tanks that had been placed near a pipe bomb.
Authorities said concerns were heightened by the fact the incident occurred on the 12th anniversary of the Columbine school massacre, in which two heavily armed teens shot and killed 12 fellow students, a teacher and finally themselves.
The two Columbine assailants, Dylan Klebold and Eric Harris, also had brought to school pipe bombs and propane tanks fashioned into explosive devices that they failed to detonate.
Mink acknowledged a similarity with the makeshift propane bomb found at the mall, but he added, "There's not a definite link we have right now to what happened at Columbine, other than the circumstances, the timing and proximity."
Jim Yacone, special agent in charge of the FBI office in Denver, declined to discuss the makeup or strength of the mall bomb, or to give further details about the man sought for questioning, saying to do so could compromise the investigation.
Mink said no one had claimed responsibility for the bomb.
Jacki Kelley, spokeswoman for the sheriff's office, said on Wednesday that federal agents were treating placement of the bomb as an act of "domestic terrorism." An FBI spokesman later said investigators believe the pipe bomb was intended to trigger a larger explosion of the propane tanks.
Kelley said the bomb fell apart while explosives technicians were handling the device as they prepared to detonate it, and it was "rendered safe."
Authorities said the mall was reopened on Thursday after police and federal agents and thoroughly combed through the facility and found no other threats. Other shopping malls in the area were alerted to the situation on Wednesday.
(Writing by Steve Gorman; Editing by Dan Whitcomb and Jerry Norton)