BRUSSELS—Belgian police had numerous chances to unmask the Islamic State terror cell that later carried out the Paris and Brussels attacks, according to a confidential report prepared for Belgium’s Parliament. They muffed every one.

In early 2015, Brussels police stopped a car driven by Brahim Abdeslam, later one of the Paris attackers, and arrested him for drug possession. At the time, Brahim was on a terror watch list. He carried a booklet about “parental consent for the Jihad.” Police found a USB thumb drive hidden behind his car radio.

He was let go after brief questioning. Authorities failed to analyze the thumb drive or other electronics seized after the drug stop from an apartment Brahim shared with his younger brother, also involved in the attacks, Salah Abdeslam. Another unnoticed detail: The email address the suspect supplied, s_orry@hotmail.com, was a fake.

The incident, details of which haven’t been previously reported, is outlined in the parliamentary report prepared by Comité P, a watchdog agency of former police and judicial officials auditing the work of Belgian police in the wake of the twin attacks. The 82-page report, reviewed by The Wall Street Journal, was finalized in September and hasn’t been made public.

Read the whole story from The Wall Street Journal.

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