Fake fliers purporting to be distributed by Immigration and Customs Enforcement and warning against any aid to illegal immigrants were found on cars and lampposts across Washington, D.C. Thursday morning, prompting concern by residents and ire from officials.

The fliers, which a spokeswoman for the agency called “dangerous and irresponsible,” suggest that D.C. residents should report anyone who entered the country illegally and that the city’s sanctuary policy violates federal law.

Milan Vaishnav, a resident of the Burleith neighborhood in Northwest D.C., said he found the flier on the windshield of his car Thursday morning, when he and his wife went out to take their kids to school around 7:30 a.m.

Vaishnav, 37, who works at the Carnegie Endowment for International Peace, said the flier looked official at first glance, but he noticed a grammatical error that led him to believe it might be fake. He said dozens of the fliers had been placed on cars in the vicinity of 37th and T streets Northwest and some surrounding blocks.

“It was rather unsettling to sort of see this letter with such stark language warning that if you know anything or [are] in contact with illegal aliens you are in the violation of law,” Vaishnav said.

Mayor Muriel E. Bowser quickly denounced the fliers on Twitter.

Kevin Donahue, Deputy Mayor for Public Safety, chimed in:

The mayor got several calls from concerned residents about the fliers, spokeswoman LaToya Foster said. Police Chief Peter Newsham reached out to ICE to confirm that the fliers were fake and is investigating who posted them. Employees of the Department of Public Works have been authorized to take down any they come across.

“We celebrate all D.C. residents; our neighborhoods are safer and stronger when no one is afraid to call on public officials for help,” Foster said.

Across the top, the flier reads “Sanctuary City Neighborhood Public Notice,” next to the seal of the U.S. Department of Homeland Security.

The fliers feature text from a federal law that deals with “alien smuggling, domestic transportation of unauthorized aliens, concealing or harboring unauthorized aliens, encouraging or inducing unauthorized aliens to enter the United States, and engaging in a conspiracy or aiding and abetting any of the preceding acts.”

“If you see something, say something,” the flier says at the bottom, along with a number for the U.S. Customs and Border Patrol.

“Notices like these are dangerous and irresponsible,” ICE spokeswoman Carissa Cutrell said in a statement. “Any person who actively incites panic or fear of law enforcement is doing a disservice to the community, endangering public safety and the very people they claim to support and represent.”

D.C. has had some form of a sanctuary city policy since the 1980s; D.C. police are instructed to not cooperate with federal authorities working to deport residents. Bowser reaffirmed after President Trump’s election that she would maintain that stance, and the District has also created a legal-defense fund and driver’s licenses for illegal immigrants.

Attorney General Jeff Sessions has pushed to deny federal funds to cities that do not share information with federal officials about immigrants’ citizenship or legal status. But a federal judge in California has blocked the administration from holding back anything but grant money awarded with immigration-related conditions.