A body found Tuesday in a ditch in an Iberville Parish sugar cane field is that of Lyntell Washington, an East Baton Rouge Parish school administrator who was seven months pregnant, the coroner said Thursday.

A comparison of dental records confirmed that the badly decomposed remains are Washington’s, said Dr. William “Beau” Clark, the East Baton Rouge Parish coroner.

Police had been searching for Washington, 40, since officers found her 3-year-old daughter wandering alone in a parking lot near her mother’s abandoned car in Baton Rouge on June 9. Blood was found inside the vehicle.

Baton Rouge police on Friday arrested Robert Marks, a 39-year-old assistant principal at the Baton Rouge school where Washington worked. Marks, who has not cooperated with investigators, is being held without bail at the East Baton Rouge Parish Prison on counts of aggravated kidnapping and desertion of the child.

The toddler told detectives that “Mr. Robbie” had hurt her mother and her mother was now “sleeping,” according to a Baton Rouge police report. Washington’s daughter also said she was with Marks and her mother when she heard a bang and that “mom’s in the lake,” the report says.

Cellphone records traced both Marks’ and Washington’s cellphones to the Ramah area in Iberville Parish about 9:45 p.m. Wednesday, the report says, where they remained for about 15 minutes before both phones returned to Baton Rouge. Marks’ cellphone was then traced to the area around Newcastle Avenue, where Washington’s car and daughter were discovered Thursday morning, the report says.

An extensive search of the swamps, fields and woods near Ramah on Friday were fruitless. Workers spraying pesticide in a sugar cane field just outside of Rosedale, not far from the search area, discovered the body in a ditch Tuesday morning, but authorities weren’t immediately able to identify the remains.

Marks told investigators that he and Washington were having an affair, according to a police report. A co-worker at the school where both worked said the unborn child was Marks’, and Washington had threatened to expose their relationship to his wife.

Marks told detectives he’d last seen Washington about 8 p.m. or 9 p.m. Wednesday at the Wal-Mart store in Baker, the report says.

Police are still investigating the slaying and haven’t yet determined whether to bring additional counts against Marks in the killing of Washington and her unborn child, said Baton Rouge police Cpl. L’Jean McKneely Jr.

“We’re going to revisit the evidence we have, contact him and see what happens from there,” McKneely said.

Clark said Wednesday the woman, now identified as Washington, had been shot in the head. Her unborn child died at the time of Washington’s death but did not have signs of separate trauma, Clark said.

The coroner said Thursday that DNA tests are also being conducted on the fetus.

The results could be used to determine the paternity of the child. McKneely said the Louisiana State Police Crime Lab is processing DNA evidence in the case.

Follow Bryn Stole on Twitter, @BrynStole.