Chicago police are investigating after a dead rat and a derogatory note were left in front of the office of 40th Ward Ald. Andre Vasquez Sunday night.

Police said the rat and a handwritten note were left in front of the office in the 5600 block of North Western Avenue around 7:30 p.m.

Ald. Vasquez, in a statement, said the note was taped to his door, referring to undocumented immigrants as vermin.

He said that his office will remain open as the investigation remains ongoing.

"We take these threats seriously, and are working with the Chicago Police Department to investigate. In the meantime, the 40th Ward Office will remain open. We are and will always be steadfast in our commitment to serving 40th Ward neighbors and supporting the rights of the immigrant community," said Vasquez, who chairs the City Council Committee on Immigrant and Refugee Rights.

Police said there is no one in custody.

No further information was available.