If you're arrested your in jail until you're bailed out. I'm not trying to get into with you, but can you please show me where it says they were arrested?
I read the article and didn't see anything about someone being arrested for not having a passport on them. It appears they were detained and questioned, but didn't see any arrests for not having a passport on them.
As I stated I've never heard of someone being arrested for not having a passport on them. They might be detained until they can prove their legal status, but if they are legally in the country they aren't going to be asserted for not having a passport on them.