Sources tell The Hollywood Reporter that Gugu Mbatha-Raw, who starred in Belle and appeared in Ava DuVernay's A Wrinkle in Time, and Jurnee Smolett-Bell, who appeared on the critically acclaimed WGN series Underground and recently booked a lead in HBO’s Lovecraft Country, are in the mix for Black Canary. Hidden Figures star Janelle Monae was also said to be in the running, but it is unclear if she tested for the role.

Canary, who is an expert fighter that is known for her “canary cry," has traditionally been white in the comics, but Warners is looking for diverse talent for Birds of Prey.

For the role of Huntress, Margaret Qualley (The Leftovers), Mary Elizabeth Winstead (10 Cloverfield Lane, Fargo) and Cristin Milioti (Black Mirror, How I Met Your Mother) have tested or read, sources say.

Justina Machado, who stars in Netflix's One Day at a Time and who has appeared on Jane the Virgin and The Purge: Anarchy, tested for the role of Renee Montoya. Roberta Colindrez, who starred on the Amazon series I Love Dick and Starz's Vida, also tested for the character, a lesbian detective on the Gotham City police force.

Both Canary and Huntress have appeared in several forms on the small screen, including on The CW’s Arrow.

Another role to be filled is that of Cassandra Cain. In the comics, Cain is a woman who functions as a mute and socially maladjusted assassin and who was, at one time, Batgirl. The studio is seeking to remold the character as a 12-year-old and is looking for an Asian actress for the part.

There are other potential actors for the roles, but Warners is said to be moving quickly, with decisions expected to made within two weeks. Birds of Prey is aiming to shoot at the beginning of 2019, with Cathy Yan attached to direct.

Robbie is producing along with Sue Kroll and Bryan Unkeless.