An oil spill off Cheung Chau yesterday highlighted the Government's inadequate response to marine mishaps, environmentalists and academics said. The 10-metre square oil slick was spotted at Cheung Chau's Tung Wan beach by Regional Services Department officers at 9 am. Staff poured dispersant on to the slick and warned people not to enter the water until 2 pm. No tests were taken to determine the type of oil and a Regional Services spokesman said other departments were not involved 'because it is not very serious'. 'It must have come from some kind of vessel . . . we are not going to test it, that's how we usually handle this kind of thing,' the spokesman said. 'It's a minor matter.' An Environmental Protection Department spokesman said officers searched for the spill's source but did not take samples because it had been cleaned up when they arrived. The Marine Department was notified, but did not attend. But Open University's ecology professor Dr Gordon Maxwell said the Marine Department should trace the offending boat. 'Someone's obviously dumped it there overnight and they can get away with it if there's not an immediate attempt to trace it or test the oil,' Dr Maxwell said. Professor John Hodgkiss, from the University of Hong Kong's Ecology and Biodiversity Department, said a standard emergency response was 'what we need'. 'There should be a set-down reaction [procedure] every time this type of thing happens,' he said. Friends of the Earth backed the calls in the wake of three marine mishaps in the past month. A container of ammonium chloride went overboard last week and vegetable oil leaked from a ship off Lamma Island on April 10.