Riso, a retired canine from the Alameda County Sheriff’s Department, rushed through a large bus as he chased the scent of cocaine and methamphetamine.

He sniffed out some drugs that were stashed near the steering wheel, then made his way to the outside of the vehicle. After a few moments, he let out a series of barks near a passenger-side panel.

On some days, sending a law enforcement dog to sniff out drugs is a very real scenario. But on Friday, Riso was the first contestant in a major K-9 competition, held each year in South Lake Tahoe.

The first day of the South Lake Tahoe Police Canine Association’s 6th Annual K-9 Trials took place at the BlueGo station on Shop Street. During the event, K-9 units from several states competed against each other to see which team was the most efficient at finding hidden drugs.

The competition will continue today at 9 a.m. during the patrol trial portion of the event, held at Babe Ruth Baseball Field. There, onlookers can watch the K-9 units compete in a show of obedience, agility, attacks and protection. Officers will dress up in large bite suits, and the dogs will be told to attack or stand down.

About 20 teams from more than a dozen law enforcement agencies attended the narcotics event Friday, and officials expect even more to show up for today’s competition. About 150 people watched last year’s trials.

It’s something the officers look forward to each year, South Lake Tahoe Police Department Sgt. Josh Adler said.

“We get a good turnout,” Adler said.

Money raised through T-shirt sales, donations and participant entry fees helps to fund new equipment, training and dogs, he said. Thousands of dollars are made through the event each year.

However, the trials also serve another purpose — they’re a great training opportunity, Adler said.

“At the end of the day, all of this is training,” he said.

Competing against other K-9 teams and having every move scrutinized by law enforcement professionals creates a tense environment for the dog handlers, Adler said.

“All those things build pressure,” he said, “so it’s good practice for them.”

Results of the 2013 K-9 Trials will be revealed at a private banquet tonight, and awards will be handed out to the K-9 team that scored the highest.