Max number for mutual aid event

Is there a maximum number of people outside of the team account that can be added to a mutual aid incident?  I read through the users guide and forums and all I could find was the statement, "Outside users do not count towards your total user count for your team account- you can add as many outside users as needed for a mutual aid incident".  More curious than anything, but it would be good to know if there is a maximum number just in case.