Frozen pipes, help ASAP!?

So it's 7 degrees outside and we wake up to find the cold water in the bathroom doesn't work. Hot water runs fine. How can we thaw the pipes out? The water runs in our basement and splits, one way to the kitchen and one to the bathroom (that is in an addition added to the back of our apartment). The kitchen water works fine, hot and cold. Thinking about getting a space heater to put in the little area where the crawl space is, between the storm doors leading outside and the access area to the basement. Please help ASAP!