'Criminal Minds,' the police procedural television drama, is all set to return for its Season 11 on CBS on Sept. 30. However, in the beginning of the new season, the Behavioral Analysis Unit (BAU) will be missing two important members.

Christian Today reports that according to the official Twitter account of 'Criminal Minds' and the statements of series executive producer Erica Messer, it can be assumed that filming of the upcoming season will begin soon.

Messer recently said, "Our season in the writers' room has already started on June 1, so that's our work for the beginning of season 11."

As two main characters of 'Criminal Minds' will be absent in Season 11 of the show, fans will witness plenty of changes in 'Criminal Minds' in the upcoming episodes. At the end of Season 10, fans were aware that both Kate (Jennifer Love Hewitt) and JJ (AJ Cook) are pregnant and they would miss the two actresses in Season 11.

While JJ will be absent from the show for the first five episodes, Agent Kate Callahan will not be featuring in any episode of Season 11. Moreover, as of now, it is not certain whether or not she will return for 'Criminal Minds' Season 12. Confirming this news, Messer said that JJ's return would be subject to the time when she gives birth.

According to Messer, "If she has the baby at the end of July, we'll have to figure out how much time she'll want. My guess is it will probably be the first five episodes."

As far as Kate is concerned, the executive producer has ruled out the possibilities of a replacement or killing off her character. According to Messer, they would plan something creative for the upcoming season, so that it is possible for her return to the show in Season 12. "We like people to come back and play whenever they can, so we don't kill them off," she explained.

While Messer denied the replacement angle, she indicated at the possibility of bringing back familiar faces from previous seasons of 'Criminal Mind,' introducing fun guest stars as well as new twists in the upcoming season.

Messer did not drop any specific names, but it is likely that Emily Prentiss (Paget Brewster) and Jordan Todd (Meta Golding) may feature in the upcoming season of 'Criminal Minds.' In fact, these speculations gained ground when actor Joe Mantegna, who portrays Senior SSA David Rossi, also hinted at Emily's possible return.

"Well, there's been talk of - there's a chance Paget may make an appearance now and again," the 67-year-old actor said.