MIAMI — A 10-year-old boy from a drug-ridden Miami neighborhood apparently died of a fentanyl overdose last month, becoming one of Florida’s littlest victims of the opioid crisis, authorities said Tuesday. But how he came into contact with the powerful painkiller is a mystery.

Fifth-grader Alton Banks died June 23 after a visit to the pool in the city’s Overtown section. He began vomiting at home, was found unconscious that evening and was pronounced dead at a hospital. Preliminary toxicology tests showed he had fentanyl in his system, authorities said.

“We don’t believe he got it at his home,” Miami-Dade State Attorney Katherine Fernandez Rundle said. “It could be as simple as touching it. It could have been a towel at the pool.”

She added: “We just don’t know.”

The case has underscored how frighteningly prevalent fentanyl has become — and how potent it is. Exposure to just tiny amounts can be devastating.

Investigators said Alton may been exposed to the drug on his walk home in Overtown, a poor, high-crime neighborhood where Assistant Miami Fire Chief Pete Gomez said he has seen a spike in overdoses in the past year and where needles sometimes litter the streets.

“There is an epidemic,” Gomez said. “Overtown seems to have the highest percentage of where these incidents are occurring.”

The three-block walk between the pool and Alton’s home took him down streets that appeared relatively clean Tuesday, but on the block in the other direction from his home, trash littered the pavement and empty lots.