The Trump administration sent shockwaves through the U.S. mental health and drug addiction system late Tuesday, sending hundreds of termination letters, effective immediately, for federal grants supporting health services.

Three sources said they believe total cuts to nonprofit groups, many providing street-level care to people experiencing addiction, homelessness and mental illness, could reach roughly $2 billion. NPR wasn’t able to independently confirm the scale of the grant cancellation. The U.S. Substance Abuse and Mental Health Services Administration (SAMSHA) didn’t respond to a request for clarification.