Q: Is there a limit to the number of people you can add to a group chat?

We have a group chat for our cross country team. Everyone in it has either an iPhone or an iPod. After the group chat got to 33 people, I was unable to add anymore contacts.  When I hit add contact and starting typing in a name or number, no suggestions or numbers pop up. Even when I type in someone's full phone number, the add button does not turn blue and I am unable to add any more people. So is 33 the magic number for iMessage group chats? I only need to add two more people!

Thanks