HEMET -- Hemet residents are planning to hold a rally Saturday in support of the city, where police have been victimized by multiple booby trapping incidents and an arsonist who burned four city code enforcement vehicles at City Hall.

The rally will begin at 1 p.m. at the Ramona Bowl, located at 27400 Ramona Bowl Road.

The rally was organized by Lori Van Arsdale, a former City Council member and Ramona Bowl board, and Tami Wihelm, another board member.

The latest attack on city police came Tuesday, when someone set fire to the city code enforcement trucks around 11:30 p.m. in an open parking lot at City Hall, Hemet Police Chief Richard Dana said.

Police closed off several blocks of Florida Avenue after the discovery was made. No injuries were reported.

"The four vehicles involved were demolished," Dana said.

It was not immediately known how the trucks were set ablaze, but no explosions were reported.

Investigators were looking at surveillance video to see if the suspect or suspects were caught on tape, Lt. Duane Wisehart told KTLA.

"We are going under the assumption that it is related to the same attacks previously," Wisehart said, referring to three booby trap incidents against Hemet police in recent months.

The discovery came on the heels of a threatening 911 call placed on Friday. The caller stated a police car would be blown up in the Hemet-San Jacinto area in the next 24 to 48 hours.

The caller said the attack would be in retaliation for the law enforcement sweep against the Vagos Motorcycle Club earlier in the week.

About 30 members of the Vagos, California's largest motorcycle gang, were arrested in Riverside County last Wednesday as part of a crackdown across the state and in Arizona, Nevada and Utah.

The gang specializes in methamphetamine sales, identity theft and violence, Riverside County sheriff's Capt. Walter Meyer said.

Dana said someone he believes may have been a gang member tried to get into a news conference Thursday at the district attorney's office in Riverside. The person was turned away, he said, because he didn't have a press credential.

At that news conference, Dana, District Attorney Rod Pacheco, state Attorney General Brown and others announced a $200,000 reward for information leading to the arrest and conviction of those responsible for the recent Hemet-area booby traps aimed at officers.

Hemet police have been targeted three times before since Dec. 31 by unknown assailants.

First, a natural gas pipe was shoved through a hole drilled into the roof of the gang enforcement unit's headquarters. The building filled with flammable vapor but an officer smelled the danger before anyone was hurt.

Then, a ballistic contraption was attached to a sliding security fence around the building. An officer opening the black steel gate triggered the mechanism, which sent a bullet within eight inches of his face.

In another attempted booby trap attack, some kind of explosive device was attached to a police officer's unmarked car while he went into a convenience store.

Gang enforcement officers appear to be the target of the assassination attempts, though Dana noted the devices were indiscriminate by nature and could have killed any police or law enforcement officer.

A prevalent theory for the attacks is that Vagos members were angered when members of Hemet's anti-gang task force monitored them at a funeral in a church opposite the task force's former headquarters.

The incidents have shaken a close-knit police department already demoralized by steep budget cuts that last year saw its officer numbers slashed by a quarter to 68.