(Adds details on planned maintenance, impact on prices)
SINGAPORE, Aug 22 (Reuters) - A fire which broke out atRoyal Dutch Shell's 500,000 barrels-per-day refinery onPulau Bukom island off Singapore on Friday occurred at a sectionof one of the units currently under scheduled maintenance, acompany spokeswoman said on Saturday.
The fire at the unidentified unit of the Pulau BukomManufacturing Site, Shell's largest wholly owned plant, was putout by the site's first emergency responders within an hour,Shell said.
Three of the six contract workers hospitalised with burnswere treated and discharged while the remaining three were stillbeing monitored, the spokeswoman said.
She did not elaborate on what caused the fire but added thatthere was no other impact on the site's operations.
In May, Reuters reported that Shell was planning to shutBukom's largest 210,000 bpd crude unit for one to two months inthe third quarter for planned maintenance.
The refinery saw production losses in September 2011 due toa fire that forced the company to shut down a crude unit and afluid catalytic cracker, which drove up margins of oil products.
Friday's fire at Bukom had caused gasoil spreads andexchange of futures for swaps (EFS) derivatives to firm up, aSingapore-based trader said. (Reporting by Jessica Jaganathan and Florence Tan; Editing byNick Macfie)
