Heavy rain and storms caused the outage, an official from PTTGC, PTT Group's petrochemical flagship.

The spokeswoman declined to say which units had been affected by the outage.

Industry publication ICIS reported last week that three of five crackers that PTTGC operates were shut on April 14 due to a power outage.

PTTGC operates a 280,000 barrels per day refinery and has an olefins capacity of nearly 3 million tonnes per year, according to its website.

(Reporting by Patpicha Tanakasempipat, editing by Louise Heavens)