Thousands of copies of a fake front page of The Arizona Daily Star declaring the United States at war in El Salvador were placed in the newspaper's vending machines throughout Tucson, authorities said.

Police were investigating Wednesday's hoax, and Executive Editor Steve Auslander said the morning newspaper would pursue a civil complaint alleging copyright violation against anyone caught.Charges of misdemeanor theft of service and trespassing could be brought against anyone involved, said police Lt. Brice Fuller.

The mock front page contained a headline reading, "U.S. at war in El Salvador - 70,000 killed." Another headline stating, "Rebels seize initiative in El Salvador," ran above stories condemning Reagan administration policies toward the Central American country.