A police informant dubbed "Lolo" contacted Spain's CNI intelligence agency last July but the agency concluded the information he provided them with was a montage, El Mundo reported.
The informant, who was paid monthly by the police and had to supply "extraordinary" information to get a bonus, alerted authorities about the existence of a jihadist cell that was read to carry out attacks and offered the videos as proof, it added.
After the intelligence agency showed little interest, he turned to police in Madrid who opened an investigation with the aid of "Lolo" and on December 30 arrested two Spanish men who appeared in the videos.
The interior ministry said at the time that the two men, Edrissa Ceesay Sanuwo and Samir Sennouni Mouh, had been detained for "glorifying terrorism" and "possession of war weapons and ammunition".
The authorities said the two men held an AK-47 rifle in several videos which featured Islamic State symbols and a picture of Puerta del Sol, a major square in central Madrid.
But later the two men said it was "Lolo" who came up with the ideas for the videos and put them online.
The investigating judge in charge of the case has summoned the police officers involved for questioning, a source close to the investigation told AFP.
He will decide in the coming days if the videos were in fact a montage, the source added.