The body of a Californian toddler has been found in the clothes dryer of a neighbour's home and a 14-year-old boy has been arrested on suspicion of the killing, police say.

Four-year-old Alex Christopher Mercado's body was found on Saturday, Fresno County Sheriff Margaret Mims told The Fresno Bee.

According to Mims, the boy was placed in the dryer after he was killed.

Sheriff's spokesman Chris Curtice says Alex's parents reported him missing on Friday afternoon.

Deputies joined by dozens of volunteers combed the area through the night and the boy was found in the dryer about 24 hours after he disappeared.

The suspect - whose name was not released - was arrested later in the day.