The U.S. military in Iraq has found evidence that new, more deadly roadside bombs, called shape charges, are not only being imported into the country from neighboring Iran, they are also being made locally. VOA Correspondent Alisha Ryu has this exclusive report:

Last month, Iraqi guards near the Iranian border intercepted a small shipment of lethal roadside bombs, made specifically to target American troops traveling in heavily-armored vehicles.

U.S. officials say there have been other similar shipments from Iran in the past several months.

Closely resembling the design of roadside bombs used by the Iranian-backed Hezbollah group against Israeli forces in southern Lebanon in the 1980s, some of these sophisticated devices have been seized at the border. Others have slipped through, killing and wounding dozens of U.S. troops throughout Iraq.

Now, the U.S. military believes Iraqi bomb makers are building these deadly weapons themselves. And they have set up workshops in poor, densely-populated neighborhoods, where they can easily hide their activities.

Last Thursday, VOA accompanied a unit from the U.S. Army's Third Infantry Division to one such place in the gritty industrial area of Sadr City, east of downtown Baghdad.

The soldiers walked past rows of dingy-looking garages and other shops until they found what they were looking for, a dilapidated mechanics shop, crammed with an assortment of car parts, steel pipes, and machinery for drilling. "That's why we came here. We saw the drill presses," one soldier said.

Manufactured roadside bombs, including the shape charges, are not the same as improvised explosive devices troops commonly used by Iraqi insurgents. The so-called IEDs usually are artillery shells, mortars or other military ordnance fitted with a remote detonator.

A shape charge, on the other hand, must be carefully constructed, using machinery. A shape charge concentrates its blast in one direction, maximizing the amount of force that hits the target. The most deadly designs include metal chunks, such as copper, that become high-velocity, molten slugs capable of slicing through armor.

The military says tell-tale signs that a bomb maker is working to produce shape charges include the presence of drill presses, pieces of pipes cut into specific lengths, and copper or other types of metal.

Scouring the mechanics shop in Sadr City, the soldiers discover two drill presses, more than a dozen cut pipes, and pieces of what appeared to be partially manufactured shape charges.

Explosive ordnance experts subsequently determined that the materials found in the shop were probably bits and pieces of a bomb-making assembly line, possibly strung out across several shops in the neighborhood.

The owner of the Sadr City shop was arrested and interrogated, but he would neither confirm nor deny the existence of such an assembly line.

U.S. military investigators are now trying to determine why such lethal devices are being produced in Sadr City, which is a stronghold for Shi'ite Muslims.

The bulk of Iraq's insurgency against U.S. forces in the past two years has been waged by disenfranchised Iraqi Sunni Muslims and foreign Sunni extremists.