AN EXPLOSION injured 27 persons aboard the Bahamian flag Alexandros oil tanker while it was under repair in drydock at the Elevsis shipyard 12 miles west of Athens. The fire was extinguished in 20 min. Officials suspect hydrocarbon vapors in cargo holds may have been ignited. A TANKER spilled about 157 bbl of heavy crude after colliding with a cargo ship in the Pacific Ocean about 220 miles off Tokyo because of poor visibility. Both vessels are Japanese.