Tight security will be imposed when 20 tonnes of fireworks are detonated to light the sky above Victoria Harbour on July 1. Yachts and pleasure boats jostling for the best view will be barred from a zone of at least three square kilometres, to be reserved for performance barges and rescue vessels. Two years ago, a container ship loaded with 50 tonnes of fireworks burst into flames after it collided with another vessel about three kilometres northwest of Green Island. Pyrotechnicians are planning to make the July 1 display bigger than any seen before in the territory. Display organisers are hoping to set off two 60-centimetre and at least eight 40-cm shells imported from Japan, but they still need to obtain approval from the Commissioner of Mines. Each 60-cm shell weighs 200 kilograms, takes three months to make, and costs US$10,000 (HK$77,310), so they are rarely seen in displays. The giant shells were banned from last month's Tsing Ma Bridge fireworks display after the organisers failed to guarantee safety distances. Australian company Syd Howard Fireworks International is planning to let off water shells - a type of horizontal rocket rarely used in displays for safety reasons. The shells skim 75 metres across the surface before bursting into a shower of sparks giving the impression of a half moon sitting on the waves. Director Syd Howard said: 'There are things Hong Kong people won't have seen. Once we get the approval for the big shells it will be a great show.'