Reference: http://www.alfawzan.af.org.sa/node/15714
Question: What is the ruling about the numerous jamaa’aat [established for the obligatory salaah – taking place] in a single masjid, particularly when some of them pray after the imaam has completed [the first jamaa’ah], and some others intentionally delay [their arrival] until after the imaam [has completed the first jamaa’ah], so they can pray with another jamaa’ah?
Response: This is not permissible; establishing numerous jamaa’aat in a single masjid at the same time is not permissible. There must only be a single jamaa’ah; however, if they have missed it – and have not intentionally delayed [their arrival to the masjid], then they should establish another jamaa’ah after the imaam has finished.