Three people have been arrested so far in connection with the blasts in a café in Marrakesh last month, officials said.
The blast in the Argana café that killed more than 15 foreigners included 10 French, two Canadian, a Dutch national and two Moroccans and injured a dozen others.
Although no group has claimed responsibility for the April 28 attack, it was suspected that al Qaeda was behind the blast.
A video was posted on the internet three days prior to the blast warning Morocco.
All the three arrested are of Moroccan nationality, said the interior ministry officials. No information was given as to where the three suspected were arrested.
The interior ministry officials said that that the main suspect was linked to “al-Qaeda and he made the bomb that shredded the cafe in the square of Djemaa el-Fna, which is a tourist spot.
The cafe attack was the deadliest to hit Morocco since a similar blast in Casablanca in May 2003 which killed 45 people, including some suicide bombers.
The investigations of the Marrakesh bomb revealed that the device was set off remotely, said the Morocco's interior ministry.