WATSONVILLE, Calif. -- The mother of a 3-year-old girl found dead in a Watsonville motel room pleaded not guilty Wednesday to charges that she killed her daughter, according to the Santa Cruz County District Attorney's Office.

Aptos resident Veva Virgil, 37, was formally charged Tuesday with one count murder for her daughter's death,Assistant District Attorney Ross Taylor said.

Officers were called to the Motel 6 at 125 Silver Leaf Drive around 2 p.m. Sunday after housecleaning staff reported finding the body of 3-year-old Isabella Grace Martinez.

A preliminary investigation indicated the girl died of strangulation.

Police learned that Virgil had checked into the motel room Saturday and left Sunday morning, Thompson said.

"She left and it didn't appear she had any intention of returning," he said.

Virgil was contacted and allegedly confessed to "acting alone to kill the child in a motel room at Motel 6," Thompson said.

"She was living in Aptos with her husband and she came down and rented the room and stayed at least one night," Thompson said. "She left the next day and left the child deceased in the room."

Thompson said Virgil's husband is Isabella's stepfather.

While police initially investigated the possibility that Virgil did not act alone in the killing, no other arrests have been made, Thompson said.

"We're currently not seeking any other involved parties," Thompson.

The murder is the city's third of the year. Two gang-related homicides were reported in October, Thompson said.