Prosecutors in Chicago this month have quietly dropped dozens of serious narcotics conspiracy charges stemming from stings involving fictional drug stash houses.

U.S. Attorney Zachary Fardon's office dropped the charges for 27 out of the 33 suspects who were arrested for allegedly attempting to steal drugs from stash houses that never existed.

Critics of the federal law enforcement technique say it amounts to entrapment and shows racial bias against minorities.

Filings dropping the charges offer no explanation. Neither does the prosecutor's office. An office spokesman declined comment when asked if the same charges will be dropped against the remaining defendants.

Katharine Tinto teaches law in New York. She says it's rare for U.S. attorneys to drop the same charges in separate cases. She says it suggests Chicago has reservations about the stings.