Why pressure cookers make such deadly explosive devices

A suspicious device found in New York City may be an improvised explosive device made from a household pressure cooker, according to early reports from local law enforcement.

Police retrieved the device on Saturday night on West 27th Street in Manhattan's Chelsea neighborhood. Nearby, on West 23rd Street, an explosion injured 29 people, all of whom have since left the hospital, NYPD confirmed Sunday.

SEE ALSO: Pressure cooker device removed from NYC street after robot inspects it

Law enforcement sources told reporters that the device on West 27th Street resembled the pressure cooker bombs used in the deadly Boston Marathon bombings in 2013.

NYPD has not officially confirmed any details about the device, except to say that the Bomb Squad is analyzing the package at a "secure NYPD facility in the Bronx," the department said Sunday afternoon.

A look at the pressure cooker recovered on 27th St. four blocks from the #Chelsea explosion https://t.co/nf10q2dRw9 pic.twitter.com/m82QDVsLjN

— New York Daily News (@NYDailyNews) September 18, 2016

In the kitchen, pressure cookers use an airtight lid to trap steam, which raises its cooking temperature to about 250 degrees Fahrenheit (121 degrees Celsius) -- ideal for quickly cooking vegetables, meats or soup.

The devices can vary by brand and model, but all pressure cookers generally have the same three components: a pressure regulator, to control and maintain pressure inside the cooker; a vent pipe, which allows excess pressure to be released; and a sealing ring, which creates a pressure-tight seal between the lid and the body.

These otherwise benign appliances are somewhat easy to transform into deadly weapons, the U.S. Department of Homeland Security explained in a 2004 bulletin to federal and state security officials.

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A portion of a pressure cooker bomb used in the 2013 Boston Marathon bombings.  The explosive device pierced the door panel of a sedan parked in Watertown, Mass. Credit: APAP Photo/U.S. Attorney's Office

Instead of food, explosive materials such as TNT and dynamite are placed inside the pressure cooker. Next, nails, ball bearings or other shrapnel surround the explosive materials.

Using other common devices, such as digital watches, garage door openers or cell phones, a would-be bomber can remotely trigger an electrical charge, which in turn ignites the pressure cooker's explosive contents.

The ignition quickly expands until it blows open the cooker, spitting out shrapnel with the speed and force of bullets.

"The size of the blast depends on the size of the pressure cooker and the amount of explosive placed inside," according to the Homeland Security bulletin. Pressure cooker bombs "can be as simple or as complex as the builder decides."

The suspicious device on W27St was safely removed earlier this morning by NYPD Bomb Squad to a secure police facility.

— NYPD NEWS (@NYPDnews) September 18, 2016

Preliminary evidence of the device that exploded at West 23 Street suggests it was an improvised explosive device (IED)

— NYPD NEWS (@NYPDnews) September 18, 2016

Federal authorities said that in Afghan terrorist training camps, participants frequently learn how to convert pressure cookers into improvised explosive devices.

In a 2010 memo, Homeland Security said such rudimentary devices were used frequently in Afghanistan, India, Nepal, and Pakistan, and occasionally in the United States and Europe. A failed 2010 bombing attempt in New York City's Times Square, for instance, involved a pressure cooker stuffed with 120 firecrackers.

Medical workers aid injured people following an explosion at the finish line of the 2013 Boston Marathon in Boston. Credit: AP Photo/Charles Krupa

Three years ago in Boston, brothers Dzhokhar Tsarnaev and Tamerlan Tsarnaev planted pressure cookers filled with shrapnel near the Boston Marathon finish line.

The explosions killed three people and injured at least 264 others.

George Velmahos, chief of trauma surgery at Massachusetts General Hospital, said all of the victims had "10, 20, 30, 40 pieces of shrapnel embedded in their bodies, mostly in their legs, but as high up as their necks," USA Today reported at the time.

Thankfully, nobody was killed by Saturday night's explosion in New York City.