A 21-year-old Southern California man has been arrested on suspicion of animal cruelty after his pet Chihuahua tested positive for methamphetamine, police said Monday.

Isaiah Nathaniel Sais of Fontana brought his Chihuahua, named Jack Sparrow, to an emergency center in Upland on July 5, telling the veterinarians the dog had ingested the drug after finding it in his house.

On arrival, the dog was in danger of dying, suffering from convulsions, seizures and an irregular heartbeat, veterinarian Dr. Allison Pope said.

When the drug-test results came back positive, Sais reportedly declined treatment for his dog and left the building, against Pope's advice.

Animal Services went to Sais's house shortly after this and seized the Chihuahua, who they say they found in a state of neglect.

"There was the smell of urine in his fur and his nails were over-grown," Jaime Simmons from Fontana Animal Services said, adding that Jack may have been kept indoors for months.

The case was immediately submitted to the San Bernardino Animal Cruelty Task Force and an arrest warrant issued for the owner.

"We don't know exactly how the dog ingested the meth, but it's reasonable to assume that it could have been accessible to children," Simmons said.

The dog remains in a stable condition in the emergency center and is expected to be transferred into a temporary foster home in the next few days.

Sais is being held at the West Valley Detention Center in San Bernardino. He has an unlisted phone number and it is unclear whether he has an attorney.