Dozens of dead fish washed up on Silverstrand Beach, Clear Water Bay, again yesterday and the area remained closed to swimmers. A large patch of red tide offshore, believed to have been caused by explosions which also killed the fish, measured 300 metres by 200 metres and was slowly diminishing, a Regional Services Department spokesman said. Officers collected between 30 and 40 more fish and sent samples to the Agriculture and Fisheries Department for analysis. Earlier tests on some of the 700-plus fish found dead in the area in recent days showed they had been killed by underwater explosions - an illegal practice still used by some fishermen. The explosions also encourage the growth of the algae which leads to the toxic red tide. Regional Services is awaiting the all-clear from the Environmental Protection Department to reopen the beach to swimmers. A red flag indicating the beach is dangerous for swimmers is expected to be flown again today.