Cops tell us ... one fan at Allegiant Stadium during the Chiefs vs. Niners tilt was thrown behind bars for grand larceny. Another was booked for battery on an officer. Two others, police say, were arrested for obstruction.

Of course, the final two arrestees were the duo of men who stripped off their shirts and ran onto the field during a play in the third quarter.

Both guys, we're told, were put into custody on charges of prohibited acts during a sporting event -- before they were released.

There were also several medical emergencies during the game ... cops tell us they received 56 calls regarding health scares -- adding that nine total people needed to be transported to the hospital for further evaluation.