(CNN) Construction crews blowing up parts of a national monument to make way for the border wall could be on the verge of destroying sacred burial sites, an Arizona congressman who represents the area told CNN.

But Rep. Raúl Grijalva, an Arizona Democrat, said he's still hoping the crews will change course before it's too late.

"You can't replace these things. You can't fix them once they're gone," Grijalva said. "And as someone that grew up in the borderlands, it's painful to know that this is occurring."

US Customs and Border Protection said in a statement that blasts had started in the area.

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