Leaky sunroof

It's been raining a lot and recently, my 1999 Mitsubishi Galant's sunroof started leaking. It's not so much a steady drip, but it dumps a large amount of water at once whenever I speed up or turn a corner, which leads me to believe that water is collecting somewhere. The water isn't coming in just one spot. The sunroof is leaking around the entire edge. Has anyone else experienced this problem? What's causing the leak, and will it be expensive to get fixed?

Hi, I have the same problem too. I wonder if just cleaning the sides around the sunroof to take off the debris will work. I will try today and reply