DETROIT (Reuters) - Authorities are investigating after four suspicious packages were sent to Toyota Motor Corp U.S. facilities in the past week that were later found not to contain threatening materials, a company spokesman said on Tuesday.

Toyota had received three packages since Friday and a fourth was intercepted at a post office in Princeton, Indiana, near a Toyota manufacturing plant, all from the same sender, Toyota spokesman Mike Goss said.

The automaker evacuated its North American manufacturing headquarters in Kentucky on Friday after a suspicious package was found in the mailroom, Goss said. The brief evacuation ended after officers determined the package was not a threat.

Similar packages were delivered to Toyota plants in West Virginia and Texas and uncovered in the mailrooms, but neither plant had to be evacuated, Goss said.

Goss said the FBI had been investigating the incidents since Friday and Toyota was not calling the incidents threats.

"For all we know, it could be that these packages were legitimate attempts to contact Toyota," Goss said.

Indiana State Police Sergeant Todd Ringle said authorities were called to the Princeton post office Tuesday morning because of a suspicious package addressed to Toyota.

The FBI, the post office and Indiana State Police are investigating the Tuesday incident, Ringle said.

(Reporting by Bernie Woodall and David Bailey; Editing by Richard Chang)