Mitsubishi Chemical Holdings Corp. and Asahi Kasei Corp. said Tuesday they are studying a plan to integrate the operations of their ethylene plants in Okayama Prefecture because of poor overall demand for plastics and other materials made of ethylene.

The companies are thinking of suspending one of the facilities within three years. The integrated facilities will likely be operated by joint ventures to be formed around next April, according to a joint statement.

The two plants operated by their group companies — Mitsubishi Chemical Corp. and Asahi Kasei Chemicals Corp. — are capable of producing 890,000 tons of ethylene per year.

The plants are in the Mizushima district of Kurashiki. Okayama Prefecture is home to one of the largest concentrations of industrial plants in western Japan.