Six elephants died in an accident at a national park in Thailand, officials there said Saturday.The elephants were on a steep hill near a waterfall when they fell into the water and drowned, Thailand's National Resources and Environment department said in a statement. The accident was reported Friday.One of the elephants was a 3-year-old calf, according to the department. Two other elephants were found at the edge of the waterfall alive, officials said.Badim Chansrikam, a local official, told Reuters that it appears a group of elephants was crossing a river when a smaller elephant slipped into the water and others mounted an unsuccessful rescue that also put them in peril."We understand that the elephants were trying to cross over to the other side of the river," the official said. "Probably, one of the smaller elephants might have slid and the adult ones were trying to rescue them but instead, were swept away by the water."Authorities have temporarily closed the Haew Narok Waterfall in the northeastern province of Nakhon Ratchasima.The waterfall is in Khao Yai National Park, where there are about 300 wild elephants.