Diatomaceous earth will solve the problem. It is a white powder that can be sprinkled either inside or outside where tha ants travel. This will kill the ants and other crawling critters and not harm pets or other animals.
Place Dixie cups out in the area half filled with white sugar and Borax (50/50 mix). Ants eat and bring back to next to kill the rest. Always works but may take 1-2 weeks.
The ants are coming in from the outside, so that is where you should be treating them. Take a box of Jiffy corn muffin mix, open it and sprinkle it outside the room they are in, typically the kitchen or bathroom. Do not bake this mix, just open and use it outside. The mix will be taken back to the colony and destroy the ants.
If you want to use an inside product, Terro liquid works well, but it is more time consuming and expect to see more ants because they are drawn to it. You can find Terro in DIY stores. I do use this product when I see a parade of ants going across the deck in addition to the Jiffy.
You can repeat as necessary.