FBI seeks person of interest in Colorado bomb incident
The FBI says it has identified a "person of interest" after a pipe bomb and two propane tanks were found following a fire at a shopping mall in a suburb of Denver in Colorado.
The FBI released two images of the man taken from Southwest Plaza Mall surveillance cameras on Wednesday.
Investigators are exploring a possible connection between the fire and the 12th anniversary of the Columbine massacre, which was on the same day.
No-one was injured in the mall fire.
The mall in the town of Littleton is located about two miles (3.2 km) from Columbine High School, where two student gunmen killed 13 people and themselves on 20 April 1999.
Unexploded pipe bombs and a propane tank with explosives attached were found in the school after those killings.
The fire at the Southwest Plaza Mall broke out in a service hallway near the food court on Wednesday afternoon.
Firefighters discovered a pipe bomb and two propane tanks, which did not ignite, shortly afterwards.
"The fact that has happened on 20 April, 12 years later, near the school and with similar devices is very disturbing," Jefferson County sheriff's spokeswoman Jacki Kelley said.
"It's something that can't be ignored and won't be ignored."
FBI spokesman Dave Joly said the authorities had identified the person of interest as being a white man with greying hair and a silver moustache.
Images taken from surveillance footage show a man, wearing a dark cap and striped shirt, entering a private-access stairwell in the mall and carrying a plastic bag.
Officials said there are typically some 6,000 to 10,000 people in the Southwest Plaza Mall at around noon each day.