The carpet ones that say corolla on them?
If this is the case you have two options, that i'm aware of. First off, you can go to Canadian tire and buy the stuff that cleans off sand and salt. We did this in my friends car and it was gone in a couple trys. Another option, if you local HAND car wash (do it yourself) has a carpet cleaner, you can also do it via this. By doing this, you wash the mats, and any other carpet you feel needs to be done seats included, and then simply vacume off the moisture from the shampoo. It was done on my friends cousin's car and it turned out just as well as the stuff from CT did!
I've yet to try either as a) I didn't buy the car till one of our last snow storms and b) bought the all season mats for winter use.
Hope that helps!