'Resident Evil 5' -- 16 Zombies Injured During Accident on Set

16 actors dressed as zombies were injured this morning during an accident on the Toronto set of the horror flick "Resident Evil 5" ... but the costumes were so gory, officials had a tough time assessing the REAL injuries.

Law enforcement sources tell TMZ ... the actors were on a set that was on wheels ... when the set suddenly moved, and the 16 actors plummeted roughly 20 feet down to the ground.

We're told none of the injuries appear to be life threatening -- but some of the actors are being treated for arm, leg and back injuries -- and possible broken bones.

All of the actors were transported to a local hospital.