Is it normal for china customs to hold all of your belongings if one thing is not declared

I have a friend who was coming to visit me in us from PRC and they found something in her bag they clamed was not legal to travel with her. they held her there for three days till she could post bail then held all of her belongings. I can understand them holding her passport and the item till the documents are done but cant see them holding her purse and all of her baggage. Can anyone tell me if this is normal for the chines because it not right and plane wrong.