Native American burial sites in Arizona have been blown up by construction crews building the US-Mexico border wall, according to lawmakers and tribal leaders.
Authorities confirmed that "controlled blasting" has begun in Organ Pipe Cactus National Monument, a Unesco recognised natural reserve about 185 km west of Tucson, the BBC said in a report on Tuesday.
The UN had designated Organ Pipe, also known as Monument Hill, as an International Biosphere Reserve in 1976, calling it "a pristine example of an intact Sonoran Desert ecosystem".
Officials have said that the aim of the project is to construct a 30ft-tall (9m) steel barrier that runs for 43 miles on the national park land.
Reacting to the development, Raul Grijalva, a Democrat congressman, called the destruction "sacrilegious", adding that the federal government failed to consult the Tohono O'odham Nation.
According to Grijalva, the chairman of the House Committee on Natural Resources who represents a district that encompasses the area, which shares 400 miles of border with Mexico, the 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," the BBC quoted Grijalva as saying.
Tribal chairman Ned Norris Jr told the Arizona Republic that even though the land was now controlled by the US government, "we have inhabited this area since time immemorial".
An internal report from the National Park Service has said that the border wall Trump promised during his 2015 campaign would destroy up to 22 archeological sites within Organ Pipe alone.
It was reported that the ancient saguaro cacti, which Grijalva said the O'odham people see "as the embodiment of their ancestors", has been destroyed.
The Trump administration has been able to build sections of the US-Mexico border wall on public land due to the 2005 REAL ID Act, which gives the federal government the right to waive laws that conflict with US national security policy.
In their bid to build the wall, the White House has waived dozens of laws - including ones that protected Native American graves.