(CNN) -- The electronic component visible in a law enforcement image of an intercepted suspicious shipment from Yemen appears to be a printed circuit board from a disassembled cell phone, an engineer told CNN Friday.

"This size and the shape of the PCB (printed circuit board) are typical to a handset cell phone type device," wrote Olivier Clerc, hardware application engineering manager for a large U.S.-based cell phone parts manufacturer.

Clerc prepared the e-mailed analysis of the image at CNN's request.

His analysis was supported by information from a source close to the investigation into two U.S.-bound suspicious packages, who said the devices appear to be designed to be detonated by a cell phone.

Cell phones have been widely used by terrorist groups as a means of triggering bombs.

"The component on the top right part of the device seems to be a digital camera sensor," Clerc wrote in his analysis. "The area with a rectangular grey material [held] a display that was removed."

"On the left of the device, under the two metallic shield cans are most likely the baseband processor or the display controller."

A baseband processor is critical to the function of a digital cell phone.

"There is as well a coin type cell (which) is a backup battery, and 2 Board to board connectors. On one of these connectors is plugged a keypad that was as well removed. Another metallic component on the top left of the electronic board (partly hidden under a screw) seems to be a small vibration component, used on cell phones (when vibrate mode is enabled). So this board is very likely to be the main electronic board of a cell phone device."

The source close to the investigation said a highly explosive compound known as PETN was found in both devices in amounts large enough to trigger a powerful blast.

PETN was allegedly one of the components of the bomb concealed by Umar Farouk AbdulMutallab, the Nigerian man accused of trying to set off an explosion aboard Northwest Airlines Flight 253 as it approached Detroit, Michigan, on December 25. AbdulMutallab is alleged to have been carrying 80 grams of PETN in that botched attack.

By comparison, the source said the two devices found in the United Kingdom and the United Arab Emirates on Friday contained multiple times more PETN. Just six grams of the material is enough to blow a hole in the fuselage of an aircraft.

A Google search for the numbered markings on the printed circuit board produced several links to the Bird D736 mobile phone. The D736 is a similar shape to the circuit board. The D736 is a Chinese-brand GSM two-band phone that allows the unit to work in most countries in the world, including the United States.

Clerc cautioned, however, that "it was not obvious that this board is the D736 phone."

In the law enforcement photo, the cell phone circuit board is crudely mounted with screws, metal and plastic fragments to what appears to be a stout metal case. Wires lead from the circuit board out of the frame.

Sources familiar with the investigation tell CNN that the suspicious shipments from Yemen contained computer printers. The metal case on which the circuit board is mounted would be consistent with the frame of a laser printer.

Law enforcement sources have also told CNN that explosives were packed in printer toner cartridges. A U.S. official says while the explosive was likely the highly volatile PETN, testing is ongoing.

CNN's Pam Benson, John Cunha and Paul Cruickshank contributed to this report.