A gunman boarded a school bus in the US state of Alabama, shot dead the driver and kidnapped a six-year-old, whom he is now holding in an underground bunker, local media reported on Wednesday.

WSFA television said the man boarded the bus at around 3:40 pm on Tuesday, shot the bus driver and took one of the children to an underground shelter, where police are currently communicating with him through a PVC pipe.

Police could not immediately be reached for comment, but Sergeant Rachel David of the Dothan Police Department confirmed to WSFA that an adult male had been shot during the incident and that the suspect was "not in custody."

"We are at the very beginning of this investigation," she said.

A statement from the Dale County sheriff's department later confirmed there was one fatality and said no arrests have been made, but gave no further details.

WSFA, a CNN affiliate, said area roads had been closed and three local school systems had canceled classes Wednesday over the hostage situation.