California Rep. Barbara Lee has asked the United Nations to investigate the impact of President Donald Trump’s policy of separating families at the U.S-Mexico border.

In a letter to U.N. Secretary General Antonio Guterres, Lee asked the organization to send humanitarian observers to the border, ABC7 reported.

“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,” she wrote in her letter.

Lee specifically asked that the conditions of detention facilities run by the Department of Homeland Security and the Office of Refugee Resettlement be investigated.

“As a mother, a grandmother, and as a psychiatric social worker, I am most concerned for the physical and mental well-being of children separated from their parents at their most vulnerable time,” she said.