The state Public Safety Department and Prosecutor's Office say three more officers were wounded in the clash early yesterday.
Police were guarding a truck and a pickup loaded with scrap metal heading to the city of Apatzingan. Officials say there was a sudden hail of bullets and grenades from dozens of attackers about an hour after midnight.
Authorities say the five civilians who died were burned when their vehicles were set on fire by grenades. There were no immediate arrests.