Police named one of the dead men as Ayoub Raidy, the brother of Abdellatif Raidy who blew himself up at the cafe.
The government has said Abdellatif Raidy was the leader of a group of more than 50 extremists that included an unknown number of suspected bombers. Security forces have detained more than 40 suspects since the March 11 blast.
Another bomber was identified as Mohamed Rachidi, who was wanted in connection with the murder of a police officer in 2003.
A judicial source told the AFP news agency on Wednesday that a "terrorist group is being formed and funded by Moroccans with the aim of carrying out bombings at Casablanca port and several police stations".
But some analysts have questioned the government's assertion that the attackers were "home-grown" and posed no serious threat to security because they lacked leadership and experience.
"I think there are links abroad," Mohamed Darif, a terrorism expert at Hassan II University, said. "The authorities will have to correct their interpretation after yesterday's events."
He said that he doubted Raydi's ability to build a network and acquire complex weapons and explosives expertise on his own while under government surveillance.