Four Greenpeace activists first occupied Brent Spar on 30 April 1995. In total, 25 activists, photographers and journalists were involved in this stage of occupation. They decided to cover up the Exxon logos on the platform. At this time, activists collected a sample of the contents of the Spar and sent it for testing, to determine the nature of the pollutants which the platform contained. This sample was collected incorrectly, leading to a large overestimate in the contents of the facility. Although Greenpeace quoted Shell's own estimate of the amount of heavy metals and other chemicals on board, they also claimed there were more than 5,500 tonnes of oil on the Spar – while Shell's estimate was 50 tonnes. For context, the Exxon Valdez oil spill involved around 42,000 tonnes.