Solid Hardwood, Engineered and Laminate Flooring - dark stain on the wood

Help! I'm refinishing my dining room floors. Today I sanded the floors with a rented vibrating sander (much easier to handle/control than a drum sander in my humble inexperienced opinion) -- they are natural maple. All is well with one exception -- in one spot there must have been a water leak (the area is about a foot around). I sanded all of the varnish off and went pretty deep into the wood, but it is much darker than the rest of the wood. What should I use to remove the stain -- bleach??? Any advice would be greatly appreciated.

The best method for removing water stains from wood uses oxalic acid. It's a powder you can get at any good paint store.

Mix a saturated solution in HOT water. Apply across the entire area. You should see results within 60 seconds.

Repeated applications may ne necessary for severe stains.

When subsequent applications have no effect, wipe completely dry and allow to dry overnight before proceeding further.