Static electricity in the dryer

Today, as I was taking my towels, out of the dryer, I noticed that they had static electricity. After a little research, I noticed that one of the reasons for this might be because of detergent that is left in the clothes after they come out of the washer. The detergent is removed from the clothes during the drying process, and the removal of these particles may create static electricity.  Also, the rubbing of the towels against each other might have created polarity in between them, creating static electricity, which is why I got shocked when I removed the towels from the dryer.