Exploded Bomb With Timer Relatively Sophisticated : Explosive: Device detonated under a car on an Irvine street Sunday when jarred by bomb squad robot. Experts are examining the auto.

A bomb that exploded under a parked car in Westpark on Sunday contained a relatively sophisticated electrical circuit and timer, as well as an explosive charge that rivaled the deadly power of a hand grenade, police said Monday.

Investigators said they have no suspects and doubt whether the woman who rented the car was the intended target.

“There’s no rhyme or reason to this at all,” Police Sgt. Phil Povey said. “We can’t discover a motive because we haven’t identified a truly intended target.”

Described as a metal pipe bomb attached to a clock with wires, the device was placed on the street under the gas tank of a white Buick Skylark that was parked on Alexandria near Athens. Police unintentionally triggered the blast shortly after 4 p.m. Sunday when their remote-controlled robot touched the device, originally described as a crude pipe bomb.

Bomb experts examined the car on Monday for pieces of the device that could reveal information on its construction and other clues, said Sgt. Charlie Stumph of the county bomb unit.

Because it contained an electric circuit and timer, it was “more sophisticated than your average pipe bomb,” Stumph said. “We are going to be very optimistic that we’re going to come up with good fingerprints (and that) we are going to identify the subject on this.”

The explosion ripped dime-size holes in the car body, blew out a rear tire, punctured the gas tank and rattled windows throughout the neighborhood.

Evidence shows that the device had been triggered but failed to detonate as it was designed to do, which is why it exploded immediately on being jostled, Stumph said.

“We’re just thankful that the robot jarred the thing with a slight bump and that no kid had come along and seen the thing and picked it up. There’s no doubt in my mind that if someone had tried to move it, it probably would have gone off” and possibly killed someone, Stumph said.

Police said the woman who rented the car, who asked that her name not be used, had been on her way to lunch at about 2:15 p.m. with a companion when they saw the device and ran back to her house to report it. She had parked the car on the street on Saturday afternoon and had not seen a device on the street at that time. At least one person saw the device as early as 9 a.m. on Sunday but failed to report it, despite thinking that it looked suspicious, police said.

Povey said his department will wait for the report from the county bomb unit, which is expected today, before pursuing the investigation.

Police said the penalty for placing or exploding a destructive device is three to seven years in prison.

People with any information that could help police are encouraged to call (714) 724-7000.

Bomb Removal During the last five years, the Orange County Sheriff’s Department bomb squad has disarmed an average of more than one bomb per week. Sources: Orange County Sheriff’s Department; Researched by APRIL JACKSON / Los Angeles Times