The Consumer Product Safety Commission warned yesterday that some popular imported fireworks being purchased for July Fourth celebrations can explode and seriously hurt bystanders.

Specifically, the CPSC took aim in its annual fireworks alert to consumers at a firework mortar shell imported from the People's Republic of China and sold under the labels of New Festival Ball and the Silvery-Eagle Ball.

According to CPSC tests, as many as 45 percent of the 3 1/2-inch, six-sided fireworks fail, spewing bursts of flame and sparks in random directions along the ground instead of into the air. This presents a very serious safety and fire hazard to users and bystanders, the CPSC said.

CPSC officials urged consumers who have purchased the New Festival Ball or Silvery-Eagle Ball to return them to the retailer--or to soak them in water for three hours and then discard them.

Last year more than 11,000 people were injured seriously enough by fireworks to require treatment in hospital emergency rooms. Most of the injuries involved children and teenagers.

To avoid mishaps this year, the CPSC cautioned consumers to:

* Buy only "Class C" common fireworks, making sure the manufacturer's label and instructions are on the firework device. Illegally manufactured devices rarely have a manufacturer's label or instructions.

* Store fireworks in a dry, cool place and avoid rough handling that might damage the fuses.

* Prohibit young children from handling fireworks and make sure adults are present when older children light the fireworks.

* Soak any malfunctioning device with water to prevent reuse.