WASHINGTON (AP) — The Justice Department has sent a letter to Alabama police agencies warning them not discriminate against Latinos as they enforce the state’s tough new immigration law.

Assistant Attorney General Thomas Perez, who heads DOJ’s civil rights division, sent the letter last week to Alabama’s 156 police agencies that receive federal funding. Perez warned that agencies risk losing funding if they violate federal policies barring discrimination. He also said DOJ officials are monitoring the law’s implementation to ensure there are no civil rights violations.

The Obama administration has sued Alabama to block the law that allows local police to detain people suspected of being in the country illegally. Parts of the controversial law have been blocked by a federal judge, but police can still arrest suspected illegal immigrants.