(Reuters) - Police in Alabama arrested a man after finding 14 grams of heroin hidden in his 2-year-old daughter's diaper, a discovery aided by a tip from the girl's 5-year-old sister, authorities said on Tuesday.

Narcotics detectives in the Birmingham suburb of Irondale pulled over the car driven by 23-year-old Kenneth Bell on Dec. 8 on suspicion he was moving drugs, said Irondale Police spokesman Detective Michael Mangina.

A drug-sniffing dog detected the presence of narcotics in the car, and police ordered Bell, his two daughters and their mother out of the vehicle.

Bell's elder daughter then told detectives that "Daddy put something in sister's diaper," Mangina said.

Police had the girls' mother undress the toddler, at which point they saw a bulge in her diaper caused by a bag of heroin, with an estimated street value of $2,500, Mangina said.

Bell was arrested on charges of chemical endangerment of a child and drug trafficking, Mangina said. He was later freed after posting $25,000 bail.

"This is somebody that shouldn't even have fathered children," Mangina said. "He needs to own up to his own mistakes, and certainly not involve his children, who are babies, basically."

The children were released to their mother, who was not arrested, and state child welfare officials are investigating the case, Mangina said.

Prosecutors and child welfare officials did not immediately respond to messages seeking comment, and Bell's attorney could not immediately be reached.

(Reporting by Jonathan Kaminsky in New Orleans; Editing by Cynthia Johnston and Peter Cooney)