KENNETT, Mo. » A southeast Missouri man told authorities he suffocated a 3-year-old neighbor girl he found playing at his backyard swimming pool and then threw her body in a floodway ditch, court documents allege.

Shawn Morgan, 43, was charged over the weekend with first-degree murder, armed criminal action and tampering with evidence in connection with the disappearance of Breeann Rodriguez.

The child was last seen Aug. 6 in front of her home near Senath, a town of about 1,500 residents located about 200 miles south of St. Louis in southeast Missouri. Her body has not been found.

Authorities said in a probable cause statement that Morgan admitted to an agent of the Bootheel Drug Task Force that he grabbed Breeann and took her inside his home after finding her standing on the ladder of his pool. Morgan said he suffocated her with a white plastic trash bag and that it "felt like it took an hour for the girl to die," according to the probable cause statement.

Morgan told police he then tossed the girl’s body in the same trash bag he used to suffocate her and threw it over a railing along Missouri 164 and into a floodway ditch.

He said that when he got home, he dismantled the bicycle the girl had ridden earlier and tossed it in the same water system as the body. A bike found in the water system has been identified as belonging to the girl.

Dunklin County Sheriff Bol Holder told ABCNews.com that investigators were looking for the girl’s body in a series of ditches in Hornersville, about six miles from Senath.

"We’re dragging the ditches, have helicopters and dogs out there searching. We’re making every effort to find her," Holder said.

Morgan was being held without bond. No attorney was listed for him in online court records, and a phone listed under his name was disconnected. A jailer said he couldn’t get a message to Morgan.

His arraignment was scheduled for Tuesday in Dunklin County Circuit Court in Kennett.