Ants from the AC

We have this weird problem with the air conditioner at the office. Whenever you turn on the AC, 30 seconds after the fan starts, big black ants start spewing out of the mouth. I think the outside pipe might be too close to the ground, the ants made a colony in the pipe, or they are collecting the dirt accumulated in the AC (which was recently cleaned, actually). But this afternoon, when we turned on the AC, instead of the 4-6 blown out, 25-30 actually came out. Let me just tell you it was quite a messy extermination...