WARSAW (Reuters) - A coal dust explosion hit Poland's top utility PGE Turow lignite power plant late on Tuesday, sparking a fire that caused a shutdown of three out of eight blocks of the plant responsible for 7 percent of the country's power supply.

Thirty-five units of firemen were fighting the blaze after the blast at the 2.1 gigawatt plant's coal transportation system that lightly injured four, but causing no casualties.

The firemen and staff were assessing the damage that potentially could cause a power deficit in the southwestern part of European Union's largest eastern member.

"The power blocks are not on fire," Roman Walkowiak, the plant's director, told state television. He said the explosion was caused by coal dust.

"If the coal transportation system for blocks 5 and 6 is damaged then there might be a problem in southwestern Poland and the power shortage may by large," Walkowiak added.

One of the blocks had been shut down earlier due to maintenance at the plant in the city of Bogatynia.

Turow is one of Poland's most modern plants after a complete make-over that finished in 2005.

(Reporting by Marcin Goettig; editing by M.D. Golan)