Pallavi Dhawan, 38, has been charged with murder of her son at their suburban Dallas home and police said she nodded her head when asked if she had killed her son - an account her attorney vehemently denies.
Police said the grisly incident unfolded after Pallavi's husband, Sumeet Dhawan, called police on Wednesday night after he returned home from a three-week business trip and found his wife gone, the New York Daily News reported.
Sumeet told police he had received emails from the boy's school, saying the fifth grader had been absent for several days.
Pallavi returned to the Frisco house while police was there, authorities were quoted as saying.
During a conversation, the boy's father grew upset and directed police toward a locked bathroom door, the report said.
Police found the child's body in the tub, covered in a sheet up to his neck.
Pallavi's attorney David Finn said that the boy had medical problems and he will seek an outside opinion on the cause of the child's death.
She was charged with murder on Thursday and was released from the Frisco City Jail early on Friday after posting bond set at USD 50,000, a report in the Dallas Morning News said.
Her husband Sumeet told police that his wife is coping with mental health issues and that the couple was having marital problems, according to a search warrant affidavit.
The Collin County medical examiner's office has not ruled on the cause of the death, pending the results of a toxicology report.
"They're from India. It's an arranged marriage. They're both Hindu," Finn was quoted as saying.
There was no evidence of fluid in the boy's lungs to indicate drowning, nor was there any trauma to the body, he said.