* Fire not affects sole 150,000 bpd CDU
* Alkylation unit shut for investigation (Adds details)
TOKYO Feb 23 (Reuters) - A fire which hit a gasoline-making alkylation unit at the Mizushima-A refinery in western Japan temporarily halted some product shipments but did not stop the sole 150,000 barrels per day (bpd) crude distillation unit, a spokeswoman at Nippon Oil & Energy Corp , Japan's top oil refiner, said on Thursday.
The fire had broke out shortly before noon on Thursday at a compresser of the 9,300 bdp alkylation unit, but was extinguished about 20 minutes later.
The alkylation unit remained shut for an investigation to find the cause of the fire, and it is not yet clear when the unit will be restarted, the spokeswoman said.
She declined to comment on the impact of the fire on the refinery's other secondary units.
There were no injuries and Thursday's fire had nothing to do with a project underway since 2010 to connect Mizushima refinery-B to refinery-A by an underwater tunnel, which was flooded by seawater in a deadly accident on Feb. 7, the company said. (Reporting by Osamu Tsukimori and Risa Maeda; Editing by Michael Watson and Ed Lane)