Police found materials with IS propaganda at Paris knife attacker's house

French investigators have found a flash drive carrying materials with Islamic State terror group propaganda during checks at a house of the man who stabbed four colleagues to death at the Paris police headquarters earlier in October, media reported on Monday.

According to media reports, Michael Harpon, 45, converted to Islam some time ago and showed signs of radicalization, including an endorsement of a 2015 terrorist attack on Charlie Hebdo journalists, but was never formally reported.

On Thursday, Harpon attacked his colleagues at the prefecture of the police in the centre of the French capital.

The flash drive contained numerous video clips with IS propaganda along with addresses and personal data of Harpon's colleagues, Le Parisien newspaper reported.

The probe into the murders that shocked France had been taken over by anti-terrorist prosecutors after it was revealed that Harpon, an IT expert, had shown signs of radicalization.