I have a gas leak from a "non visible" source in a small-ish kitchen. About how much would it cost to fix?

I've had it checked this morning - it is not from the cooker or boiler so it must be under the floor or behind the wall or something. Nightmare. Do you think it would be multiple �1000s or multiple �100s to fix? Either way it needs to be done. Obviously. Does buildings insurance typically cover this?