Update: On Friday, the Humane Society doubled the reward to $1,000.

The Oregon Humane Society is offering a $500 reward for information leading to the arrest of whoever killed a dog by dropping it into Clackamas River trapped in a plastic pet carrier sometime last month.

On the morning of Dec. 18, the Clackamas County Sheriff's Office discovered the body of the female Chihuahua, still inside the pet carrier, submerged in the water near the Carver Park boat ramp.

Authorities believe the animal was either put in the water at the boat ramp or dropped from the nearby Carver Bridge, which crosses the river at Springwater Road. The animal appeared to be in good health before it died and was well groomed, the Humane Society said in a press release.

She likely died soon before she was discovered.

The dog had brown fur with black markings and a black muzzle. She was wearing a collar, but had neither ID tags nor a microchip.

Putting a live animal in a river with the intention of killing it is a felony, according to the Humane Society, who is partnering with the sheriff's office and Clackamas County Dog Services on the investigation.

Anyone with information about the incident or who saw suspicious activity in the area around the time the dog was discovered was asked to contact the Humane Society at (503) 285-7722 ext. 214 or by submitting a tip here.

-- Kale Williams

kwilliams@oregonian.com

503-294-4048