Native American burial sites have been blown up by construction crews building the US-Mexico border wall. Authorities confirmed that controlled blasting" has begun at Arizona's Organ Pipe Cactus National Monument, a Unesco recognised natural reserve. Raul Grijalva, a Democratic congressman, told the Intercept the destruction is "sacrilegious". The government failed to consult the Tohono O'odham Nation, he said. Environmental groups also warn of the damage being done to the local underground aquifer, as well as to migrating wildlife. Officials say the aim of the project is to construct a 30ft-tall (9m) steel barrier that runs for 43 miles on the national park land. The United Nations designated Organ Pipe as an International Biosphere Reserve in 1976, calling it "a pristine example of an intact Sonoran Desert ecosystem". Mr Grijalva, the chairman of the House Committee on Natural Resources, represents a district that encompasses the area, which shares 400 miles of border with Mexico. He toured the burial sites at the Organ Pipe, known as Monument Hill, last month, and was told that O'odham people buried warriors from the rival Apache tribe there. "What we saw on Monument Hill was opposing tribes who were respectfully laid to rest - that is the one being blasted with dynamite," Mr Grijalva said. He called the Trump administration's conduct "sacrilegious" and said the environmental monitor that the government assigned to the project would do nothing to mitigate the cultural damage.