Rep. Barbara Lee (D-CA), who is running to be the House Democratic Caucus Chair on Wednesday, again called for United Nations inspectors to go the U.S.-Mexico border after border patrol agents on Sunday fired tear gas at migrants who were pelting them with rocks.

Lee said on Monday that she was calling for U.N. inspectors at the border because “the tear-gassing of women and children at the border is an atrocity” and “a violation of human rights.”

“And it is a grotesque betrayal of our founding promise, as a nation built by immigrants,” she continued.

When the Trump administration was separating families at the border earlier in the year, Lee wrote to United Nations Secretary General António Guterres and requested “humanitarian observers” to investigate the Trump administration border and family separation polices.

“I am appalled by the reports and images from detention facilities in Texas and other states along the border, where more than 2,300 children have been separated from their parents by border patrol agents,” Lee wrote then. “I urge you to send experts from relevant UN agencies to observe conditions in both Department of Homeland Security (DHS) and Office of Refugee Resettlement (ORR) facilities both at the border and throughout the more than 17 states around the country that are now housing children who have been separated from their families.“