(RNN) - Atlanta's Hartsfield-Jackson airport being shut down while authorities made sure a food cooker wasn't a bomb was not as unusual a precaution as it may sound like.
A "pressure-cooker bomb" that exploded in April 2013 at the Boston Marathon, killing three and wounding hundreds more, has been used by terrorists in India, Pakistan, Afghanistan and Nepal according to an unclassified document released by Homeland Security in 2010.
That same year, instructions on how to construct the bombs were published in an online magazine with Al-Qaeda ties, and multiple websites contain the same information.
The Homeland Security document warned the bombs were portable and easy to transport and conceal.
"Terrorists can exploit the innocuous appearance of easily transportable items such as pressure cookers to conceal IED components. Placed carefully, such devices provide little or no indication of an impending attack," the document said.
Similar bombs were used in the Mumbai train explosions that killed about 200 people in 2006. The same sorts of bombs were used in the 2010 attacks on Times Square and on World Vision International in Pakistan.
At the Boston bombing, Associated Press reported that 6-liter pressure cookers filled with ball bearings and metal was hidden inside duffel bags and left at the scene of the explosion.
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