Why would ants die after eating corn chips?

Recently, a small army of ants attacked my pantry and found a bag of chips i had just purchase and just opened the day before. These were a nationwide brand of corn tortilla rounds in a 2lb bag. Just before eating again from the bag I noticed that each chip had a small pile of 20-30 dead ants sort of stuck to the chip and each other. What (kind of) ingredient in a common tortilla corn chip would kill an army of ants instantaneously? any ideas?