Police arrested the suspect in the city of Casablanca, a source close to the investigation of the attacks said without giving further details, Reuters reported on Wednesday.
At least 16 people died as a result of terrorist attack in the Spanish city of Barcelona and the nearby town of Cambrils on August 17 and 18.
Spain’s Interior Minister Juan Ignacio Zoido said on Tuesday that Moroccan authorities had arrested two people linked to the terror cell, without giving further details about them.
Spanish news agency EFE said the second man had been arrested in the city of Oujda and was a relative of one of the members of the Barcelona cell.
The source cited in Reuters’ report did not confirm a second arrest.
The Moroccan supplier had given the terrorist cell around 120 canisters of butane gas, which they had stocked in a house in the southern Spanish town of Alcanar. The terrorists had reportedly been planning to use the gas canisters for major bombings in Barcelona.
Police believe members of the cell accidentally ignited the gas canisters on August 16, the eve of the Barcelona attack, triggering a blast that killed two of the terrorists and destroyed the house in Alcanar.
The remaining attackers then decided to launch a car ramming attack along Barcelona’s Rambla Avenue and later mount a similar assault in the resort town of Cambrils.
Most of the suspected attackers were Moroccan.
Apart from the two terrorists who died in the explosion in Alcanar, six were also shot dead by police. Four other people were arrested over the assaults, two of whom have now been released under special conditions.
The attacks were claimed by the Takfiri Daesh terrorist group.