Korean prosecutors on Tuesday raided the offices of eight local firms that manufacture construction materials to determine if they rigged prices of their products.

The move aims to determine if companies deliberately fixed prices that distorted the free market and hurt other firms and consumers that used their products.

Investigators raided offices of the firms and homes of senior executives, and confiscated documents and other materials, which they think will help determine the validity of the price-rigging allegations.

These firms specialize in the production of "prestressed high-strength concrete" (PHC) piles necessary to prop up structures on weak foundations. The PHC pile market is estimated to be worth around 500 billion ($419 million) annually.

After analyzing the evidence they confiscated, the prosecutors are expected to summon top officials of the companies for questioning. (Yonhap)