Invaded by ants!? our back garden is invaded by millions of ants and we...

our back garden is invaded by millions of ants and we cannot find where on earth they are coming from - we put down insecticide (ant powder) but it affected my cat who be very poorly so reluctant to use again - what smaller amount harmful product/thing can we do to exterminate then?
In my tub I own these bugs that...
turn to the diy store and get some ant bait ur cat cant attain into it but the ants can get within and they take woteva it is stern to the nest and kills them.
Does this nouns approaching too much for an...

Electric cooker or a gas hob?
If you are trying to control them outside, I would use a pyrethroid spray. Bayer Advanced has a nice one call Multi Insect Killer. It comes in a ready-to-spray formula. I would keep hold of your cat out of it until the spray dries and then you should be O.K. If you are trying to grasp them out of the house I would use an ant bait product. I wouldn't use products that aren't registered by the EPA like another poster have recommended. They probably won't work and may have other unintended consequences.

OldeHippy make a great point. If they are suger feeding ants, those outdoor bait work well too.
How can you keep hold of the heat...
Answers:    Home Depot sell "ant traps", small plastic packages containing a liquid that the ants transport wager on to their nest to feed young at heart. Faced with a problem similar to yours, we placed six of these "traps" (they come within a box of 6) along the routes the ants seemed to be following. Three days latter, the ants were gone.
It be interesting to watch on the second time as the ants set up columns to transport the "food" back to the nest. Hundreds of ants march single file surrounded by double rows coming and going to the "food source".

Good luck.