BRENTWOOD -- A man buying a $3 chocolate treat from an ice cream truck got an extra something with his change -- a baggie of methamphetamine, authorities said.

It could have been an innocent mistake, according to police, but the ice cream man was arrested and prosecutors will ultimately decide if he should be charged.

The 30-year-old Brentwood man told police he took a break from working on his pickup truck at about 3 p.m. Wednesday on the 200 block of Mountain View Drive to cool off with some ice cream.

When he handed the suspect $20, a dime-bag size of meth was tucked in his $17 in change.

After the man said he didn't want the drug, the suspect replied he didn't know how the baggie ended up in his truck and asked the man to throw it away, according to police.

The man kept the bag and called police.

Five minutes later, officers found 62-year-old Kelly Brown of Oakley and his truck at a gas station at John Muir Parkway and Balfour Road. Brown repeated to officers that he does not sell drugs, and theorized the bag of meth could have come from a customer earlier in the day.

Brown was arrested on suspicion of possession and transportation of methamphetamine, both felonies.

He was booked at Martinez Detention Facility. The case will be sent to the Contra Costa District Attorney's Office for review. Lt. Doug Silva of Brentwood police called it an isolated case and said they have no reports of similar incidents involving Brown.

"It's very possible he could have accepted this from someone else," Silva said.

There were no children involved in the incident, police said.

David DeBolt covers breaking news. Contact him in Richmond at 510-262-2728. Follow him at Twitter.com/daviddebolt.