SEOUL -- South Korea's police special forces were searching the building of the ruling People Power Party in central Seoul after a threat of planting explosives, multiple media outlets said Thursday.

It was reported to the police at about 11:00 am local time (0200 GMT) that the People Power Party received a fax of threatening to install explosives in its building from an unidentified person.

The police dispatched special forces and detection dogs to search inside and outside the party's building.

Neither an explosive device nor other material had yet to be found. The police were investigating the fax sender and other details.