An 8-month-old boy was hospitalized in Fort Worth after methamphetamine and other drugs were found in his system.

The infant was in stable condition Friday. Lab results showed the baby tested positive for amphetamine, methamphetamine, nicotine and caffeine, Richland Hills police Detective Tye Bell said.

"The doctor's opinion was this baby was drugged sometime Thursday and the amount was significant," Bell said.

Child Protective Services has taken custody of the baby, along with his 20-month-old sister.

The boy's mother, Whitney Walker, rushed her son to North Hills Hospital in Richland Hills on Thursday when she noticed he was acting unusual and was unresponsive during a visit at his grandmother's house in the 3100 block of Rufe Snow Drive in Richland Hills, police said. The boy was later transferred to Cook Children's Medical Center in Fort Worth.

Bell said Walker, 21, left her children with her mother, Janna Beau, for about four hours starting at 10:30 a.m. Thursday. She said her son was fine when she left. She returned about 2 p.m. and realized something was wrong.

Walker told police she gave her son a prescribed antihistamine for a respiratory infection before she left. Beau, 48, said she put Vicks VapoRub on the boy while his mother was gone.

The Richland Hills Police Department's K9 unit searched the grandmother's house, but no illegal narcotics were found. Detective Bell said police have been called to the house many times before for family violence.

"Both grandmother and mother have an assaultive criminal history," he said. "Neither one has drug-related charges."

Police are investigating how the baby ingested the drugs.

"I have been thinking about that," Detective Bell said. "I cannot think of any method for an 8-month-old to have these four chemicals in his body without somebody putting them in him ... with the exception of the nicotine, [which] is possibly from secondhand smoke."

Detective Bell said doctors believe the boy's long-term prognosis is good. He said CPS plans to have the boy's sister undergo tests to check for any drugs in her system.

Police continue to investigate, and no arrests have been made.