A gunman injured six people at a FedEx warehouse Tuesday before killing himself in the U.S. state of Georgia, local media reported.

An active shooter at the suburban facility in Kennesaw, about 40 km north of Atlanta, was reported to police at around 5:54 a.m. and one of the injured was in critical condition, according to the report.

"The suspect in this case is deceased from an apparent self-inflicted gunshot wound," the police said in a statement.

A FedEx spokesman said the company was cooperating with authorities.

The police were investigating the cause the incident.