A Houston mother who calmly told an acquaintance that she had drowned her two children in a bathtub has been charged in their deaths and was being held without bond Monday.

Sheborah Thomas, 30, was charged Sunday with capital murder of a person under age 6, according to court records.

"All indications are she is the one who acted alone" in the deaths of her 7-year-old son and 5-year-old daughter, Houston police spokesman Kese Smith told The Associated Press. Their bodies were found Sunday under a neighbor's house.

Authorities have not yet confirmed a cause of death but said an acquaintance of the woman told police she said she drowned her children in a bathtub.

Smith said investigators are still interviewing the woman and have not determined a motive. Autopsies have been ordered.

Online criminal court records do not list an attorney to comment on behalf of Thomas.

The acquaintance told authorities he came across Thomas dumping trash in a field and that she told him she needed help moving right away. When the man asked about her kids, she calmly said she had killed them, Smith said.

"She was so matter-of-fact about it, he didn't think she was serious. He thought she was joking," Smith said. "He continued to help her pack."

Smith said the man eventually realized something was wrong when he asked again and got the same answer. He then drove the woman to a nearby police precinct and flagged down an officer, Smith said.

The mother apparently tried to bury the children but when that proved too difficult she hid their bodies under a neighbor's house, Smith said.

Smith said investigators don't yet know if the mother has a history of mental problems. He said police had been to the home before but for "nothing major."

Tejal Patel, a spokeswoman for the Texas Department of Family and Protective Services, said state child welfare officials have visited the family, but that she could not disclose the nature of those visits. Patel said a "top to bottom review" of the family will be conducted.

Neighbors told the Houston Chronicle that the family had moved in just a few months earlier.

"She would just take her kids to the park; that's all everyone saw of them," neighbor Mike Polk told the newspaper.

In 2001, Houston mother Andrea Yates drowned her five children ranging in age from 7 years to 6 months in the bathtub of her family's home. She was eventually found not guilty by reason of insanity in July 2006 and sent to a state mental hospital.

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