UPDATE 1-Tosoh's monomer plant caught fire after explosion

* One worker still missing

* Fire occurs at No.2 vinyl chloride monomer plant

* No schedule of when fire can be put out (Adds details, Idemitsu comment)

TOKYO, Nov 13 (Reuters) - Fire broke out after an explosion shortly before 3:30 p.m. (0630 GMT) on Sunday at a vinyl chloride monomer plant at Tosoh Corp's Nanyo complex in Yamaguchi prefecture, western Japan, a company official said.

The company and the fire department have been trying to put out the fire at the No.2 vinyl chloride monomer plant. The cause was not known, the official said.

Television footage showed plumes of black smoke. One worker was missing, a fire department official said.

The fire department sent 11 fire engines to the scene, but it was not clear when the fire could be brought under control, the official said.

Tosoh's Nanyo complex, which operates three vinyl chloride monomer manufacturing plants, is capable of making a total 1.2 million tonnes per year of the material used in making plastic , the Tosoh official said.

The No.2 plant can make 550,000 tonnes a year. The No.1 and No.3 plants are capable of manufacturing 250,000 tonnes and 400,000 tonnes per year, respectively, the Tosoh official added.

Following the outbreak of the fire, oil refiner and ethylene producer Idemitsu Kosan Co significantly lowered its pipeline supply of ethylene to Tosoh from its Tokuyama plant, an Idemitsu official said.

Idemitsu also will reduce its output at its 623,000 tonnes per year naphtha cracker at Tokuyama plant but will keep supplying steady volumes to other customers, the Idemitsu official added.

(Reporting by Osamu Tsukimori; Editing by Robert Birsel)