By Marice Richter

DALLAS (Reuters) - A man and woman discovered dead in a suburban Dallas home were the parents of a 10-year-old boy found dead in January in a bathtub at the same residence, leading to the arrest of the mother, the family's lawyer said on Thursday.

Police have not yet officially identified the bodies found on Wednesday in the suburb of Frisco. Attorney David Finn said he was contacted by relatives of Sumeet and Pallavi Dhawan, parents of the dead child, asking for his assistance in returning their bodies to their native India.

Frisco police were called to the home to investigate a possible drowning. One of the bodies was discovered in the swimming pool and the other inside the house.

Pallavi Dhawan was arrested for killing her son after police discovered the boy's partially decomposed body in a bathtub surrounded by ice packs. She was released on $50,000 bail.

The couple had told investigators their son died of natural causes from a medical condition.

The Collin County Medical Examiner did not determine a cause of death for the boy.

"Their toxicology report was clean and there were no signs of trauma, smothering or drowning in the autopsy," Finn said.

"This was a mother who loved her son. She placed his favorite toys around the bathtub."

The boy died while the father was on a business trip and the mother attempted to preserve the body to follow Hindu custom, Finn said.

A Collin County justice of the peace ruled in August there was enough evidence for police to investigate the death as a homicide. Witnesses had been summoned to testify before a grand jury.

(Reporting by Marice Richter; Writing by Jon Herskovitz; Editing by Eric Beech)