BANGKOK, Nov. 1 (Xinhua) -- A hydrogen tank exploded in north Thailand's Tak province early Sunday, killing at least one, injured over 30, media said.

    The accident happened when a hydrogen tank for filling balloons exploded at a "Loi Krathong Festival" in the province's Mae Ramad district, the Channel 7 quoted local police sources as saying.

    Police said the explosion occurred around 01:00 a.m. and a balloons vendor was killed, some five people seriously injured.

    "Loi Krathong" is held on the full moon of the 12th month in the traditional Thai lunar calendar. In the western calendar this usually falls in November.

    This year's festival opened in the capital of Bangkok on Saturday night with thousands of Thai people and foreigners joining the event.

    "Loi" means "to float". "Krathong" is a raft about a hand span in diameter traditionally made from a section of banana tree trunk(although modern-day versions use specially made bread 'flowers' and may use styrofoam), decorated with laborately-folded banana leaves, flowers, candles, incense sticks and so on.

    On the night of the full moon, many people will release a small raft like this on a river. Governmental offices, corporations and other organizations also build much bigger and more elaborate rafts, and these are often judged in contests.

    In addition, fireworks and beauty contests take place during the festival.