DUBLIN -- Drug-sniffing dogs are returning to Dublin middle and high schools to deter students from bringing alcohol, drugs or weapons on campus.

The dogs, however, are not from the Alameda County sheriff's unit as first planned a year ago.

The Dublin Unified School District decided this year to contract with a large company that specializes in using "people friendly" dogs to sniff out illegal and prescription drugs and alcohol -- not just the illegal drugs that police dogs focus on.

The first dog from Interquest Detection Canines sniffed around Wells Intermediate School last week.

Under an agreement, the school district will pay Interquest a total of $1,300 for dog and dog handler visits during the rest of the school year.

"The purpose isn't to catch kids, but to send a strong message not to bring drugs and alcohol to campus," said Amy Miller, a Dublin school board member.

Castro Valley schools also use Interquest.

The Dublin school system cut out the canine checks in 2007 during sharp budget cuts, but the board decided in March 2012 to bring back the dogs.

School officials initially said they planned to have Dublin's police agency -- Alameda County Sheriff's Office -- perform the service for free with their dogs and handlers.

But Dublin school officials balked because the Sheriff's office wanted a "hold harmless" clause shielding the agency from liability in case a police dog injured someone, said Stephen Hanke, the Dublin schools superintendent.

"That would have exposed us to open-ended liability," Hanke said. "We didn't think that was wise."

The Interquest dogs, he said, are very "student friendly" and gentle yet efficient in sniffing out contraband.

The dogs will visit Dublin High School, Valley High continuation school, and Wells and Fallon middle schools.

Lockers will be checked at campuses with lockers, and parking lots will be checked at campuses to which students drive. Dublin High has no lockers but does have student parking.

The drug canines will not check classrooms this school year because ground rules for the visits have yet to be worked out between the district and Interquest.

According to a 2012 survey of Dublin school students, 39 percent of 11th grade students said they had gotten high on drugs at some time; 54 percent had drunk alcohol and 42 percent had smoked marijuana.

When the dogs sniff contraband, they sit in place. School officials will handle any discipline, officials said.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.