WASHINGTON — Cell phones modified so they could detonate bombs by remote control were found by investigators probing the recent Saudi Arabia bombings, raising concern that such methods could be used in the United States by terrorists.
An unspecified number of rigged cell phones turned up during searches following the May 12 bombing in Riyadh that killed 35 people, including nine Americans. The FBI said Wednesday it had no information that such devices might be used in a specific terrorist plot in the United States but urged extra vigilance.
"Law enforcement agencies should remain alert to potential use of such devices and incorporate awareness into their counterterrorism preventive measures," the FBI said in its weekly bulletin to 18,000 state and local police agencies.
The FBI urged local authorities to take precautions if such a device is found.
For instance, officers should "immediately evacuate the area to a minimum distance of 300 yards. Radios, cellular telephones and pagers should not be used within 50 feet of the suspected device," it said.
Terrorists also have used pagers and radio systems to detonate bombs by remote control, the FBI said.
The bulletin did not say whether cell phones were used in the Saudi bombings, nor were there other details about the searches that uncovered the suspicious phones. Saudi officials, who blame al-Qaida for the attack, said last week they had identified 12 of the attackers and had 25 people in custody in the case.
A cell phone was used in the July 2002 bombing at a cafeteria at Hebrew University in Jerusalem that killed seven people, including five Americans. The bomb, filled with nails and metal, was hidden in a bag left on a table in the crowded room and was detonated by a call from another cell phone.
Late last year French police found explosives systems meant to be detonated with cell phones during a series of raids around Paris that dismantled a terror group with ties to al-Qaida and rebels in Chechnya.
Experts say the cell phone provides the advantage of allowing the bomber to be far away from the explosion. Timing devices such as windup alarm clocks or radio transmitters more frequently used in improvised pipe bombs usually require the perpetrator to be closer.
The FBI bulletin said that when the phone receives an incoming call, "the electrical power from the telephone's ringer or vibrator activates the bomb's circuitry," causing an explosion.
"Law enforcement officers without specialized explosives training should never attempt to remove or disable a suspected device," the bulletin warned.
Greg Baur, chief of the International Association of Bomb Technicians and Investigators, said use of cell phones requires expertise to program the phones and handle tiny components.
He did not know of a domestic bombing case involving use of a cell phone.
"You'd have to have a lot of technological ability," said Baur, former commander of the Milwaukee police bomb squad. "It takes a certain amount of training, a certain amount of electronic knowledge."
Landline phones have been used in years past to set off smaller explosions, FBI officials say. One technique was to rig the phone so it ignited gasoline-soaked material when it rang. In many of those cases, the aim was to collect insurance money when a building burned.
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