Moroccan investigators rounded up and questioned suspected Islamic militants after a series of suicide bombings that killed 28 people, an official said.
Five "groups of kamikazes" -- 14 attackers in all -- carried out the Friday night attacks, Interior Minister Mostapha Sahel said Saturday. He said 13 bombers were killed -- making the death toll 41. A surviving, wounded attacker was being interrogated, he said.
Investigators were focusing on whether the attackers were linked to a known extremist group, Salafia Jihadia, which is suspected of belonging to the al-Qaeda terror network, an Interior Ministry official said.
The official, who spoke on condition of anonymity, said suspected Islamic militants were being questioned but that it was "too early at this stage to refer to them as arrests." It was not clear how many people were questioned.
Police set up barriers on roads into Casablanca, checking cars.
Salafia Jihadia has been the object of police sweeps for months. About 100 people found to have ties with the homegrown group were in custody as recently as March, including a suspected leader known for fiery sermons and anti-Western views.
The attacks appeared to target mainly Jewish and Spanish interests. Spain was a leading US ally in the war on Iraq.
The attacks stunned this moderate Muslim North African kingdom -- a staunch US ally and popular tourist destination -- and sowed new anguish around the world. They came just four days after similar terror attacks on Western targets in the Saudi capital of Riyadh that killed 34 people.
The bombers appeared organized and their attack carefully planned.
The interior minister said they divided into five groups in the attacks on five civilian targets -- from a Spanish social club to an old Jewish cemetery. About 100 people were injured, 14 seriously, the minister said.
The dead included two Spaniards, two French and one Italian, he said.
These "were classic terrorist targets: Jews..., tourists and foreigners," Serge Berdugo, president of the Council of the Jewish Community in Morocco, was quoted as saying by the national MAP news agency. "The goal is put us in the spiral of international terrorism."
Up to 4,000 Jews live in Morocco, and the kingdom is proud of the harmony that marks relations between its Jewish minority and Muslims.
The deadliest bombing ripped through the upscale Casa de Espana social club as clients were playing bingo or dining. Some 20 people were killed, including a guard whose throat was slit, said the club president.
The scene of horror was repeated at other downtown sites. Besides the Casa de Espana, the bombers struck a Jewish community center, a Jewish cemetery, a hotel and a Jewish-owned Italian restaurant in front of the Belgian Consulate, which was damaged.
Without directly implicating al-Qaeda, the Moroccan government laid blame on international terrorism.
Islamic fundamentalists are well installed in Morocco, especially active at universities and in the grinding poverty of cities like Casablanca -- Morocco's largest.
Militants were kept in check for decades in a careful balancing act by the late King Hassan II, who ruled for 38 years. Monarchs here bear the highly respected title of "commander of the faithful."
However, militants have grown bolder as King Mohammed VI, who took the throne in 1999, presses ahead with efforts to modernize and moves to democratize.