Denver- A volunteer with a Denver animal shelter has been arrested on suspicion of having sex with a dog, police said.

Gustavo Castanon, 33, of Denver is being held at the Denver Jail in lieu of $10,000 bail after being arrested Wednesday on suspicion of animal cruelty, a misdemeanor charge, said Sonny Jackson, a Denver police spokesman. Castanon is accused of coaxing the dog to perform oral sex.

Castanon also has been suspended from his volunteer position for “inappropriate behavior with a dog,” a shelter official said.

In 1998, Castanon was arrested for unlawful public indecency in Cheesman Park, according to court records. He pleaded guilty to the charge and paid a fine of $200 and court costs.

Officials at the Denver Municipal Animal Shelter, 678 S. Jason St., “initiated the investigation” against the volunteer, said Ellen Dumm, spokeswoman with Denver Environmental Health.

“We’ve asked for an investigation by police and the district attorney’s office,” Dumm said.

A witness told investigators that Castanon had sexual contact with a basset hound at the shelter Saturday.

Police were notified Monday. Dumm declined to go into details. She said the dog was not physically harmed.

“There’s a big yuck factor here,” Dumm said.