The takeover, which follows Wednesday's resignation of Ferguson Police Chief Thomas Jackson and the "ambush" shooting of two police officers late Wednesday night, is effective at 6:00 PM local time, St. Louis County Police said in a statement.
Ferguson Police will remain in charge of routine policing services in the city.
The arrangement will remain in place indefinitely, St. Louis Police Department spokesperson Sergeant Brian Schellman told Sputnik.
“Conversations were had with the Mayor of the city of Ferguson and our [St. Louis] police department and they [Ferguson] just don’t have the resources or manpower for it [security], and so we are going to assist them and we are going to take over security detail at this time until further notice,” Schellman said on Thursday.