A faulty timing device and a stiff wind were responsible for a fireworks accident that injured seven bystanders at the Lee District Park Independence Day celebration. Fairfax City fire officials said yesterday.

Fire officials described the accident as a "quirk" and said that county safety regulations were fully met at the time of the accident.

A timing mechanism on a fireworks rocket designed to touch off five separate blasts failed, they said, causing two blasts to fire near the ground.

The seven spectators were injured when wind currents carried the rocket toward the crowd, where it exploded the officials said.

According to fire law, spectators are required to stay at least 500 feet away from where fireworks are launched. The crowd had maintained this distance, fire officials said, but winds carried the rockets toward the front of the audience.

Those injured were taken to Mount Vernon Hospital south of Alexandria where hospital spokesman said they were given emergency treatment for minor cuts (some requiring stiches) and burns to their legs and arms. At least one person complained of a temporary hearing loss.Those injured ranged in age from 12 to 34. None required hospitalization.

Wayne Cottrill, superintendent of park facilities for the Fairfax County Park Authority, estimated that about 15,000 people attended the Fairfax display.

Also injured Monday were seven Montgomery County residents who were watching a display at Richard Montgomery High School. In that incident, smoke and debris from a rocket that exploded lower than expected fell toward a crowd estimated at 50,000.

Seven onlookers were taken to Suburban Hospital complaining of temporary inflammation or irritation of their eyes.