They had to make their way through tight security, including metal detectors and bomb-sniffing dogs.

NPR: Boston Bomb Investigation Extends To Russia

They made their way through tight security, including metal detectors and bomb-sniffing dogs.

BBC: Boston bombs: Memorial for slain officer Sean Collier

Until recently the only equipment for spotting a suitcase bomb was an unwieldy machine the size of a refrigerator, using liquid nitrogen to cool crystal detectors down to 300 degrees below zero and taking hours to produce a reading.

FORBES: Stopping Porta-Nukes

Until recently the only equipment for spotting a suitcase bomb was an unwieldy machine the size of a refrigerator that used liquid nitrogen to cool crystal detectors down to 184 degrees Celsius below zero and took hours to produce a reading.

FORBES: Stopping porta-nukes