Parliament has remained tight lipped on claims that two chauffeurs working for the institution have been sacked after being found in possession of Islamic State "propaganda material."
One of the chauffeurs allegedly worked for the Parliament in Brussels, while the other was employed at its other site in Strasbourg.
According to the German weekly news magazine 'Der Spiegel', the pair were dismissed when the discovery was made and a police investigation has been opened into the two chauffeurs' possible connections to the Isis.
Citing "informed sources", Der Spiegel says that the exact content of the propaganda material, found in the drivers' personal effects and said to include an Isis CD, has not yet been disclosed.
The two men are thought to have been employed by a Paris-based firm. This has issued a statement denying that any offending material was found on the drivers.
Der Spiegel, however, stood by the article and also said it was revealed that a number of other drivers "had serious criminal records."
On Monday, a spokesperson for Parliament declined to comment on the article, adding, "As a rule we do not comment on things touching on security."
Belgian police were not immediately available for comment.
If proven, however, the allegations will cause further acute embarrassment to the institution after it was recently revealed that one of the Brussels bombers, believed to be Najim Laachraoui, previously worked as a cleaner at the Parliament as a student summer job for a month in both 2009 and 2010. The contracted cleaner had access to every office in the building.
Last week, the Parliament approved controversial plans for a new in-house chauffeur service, which they say is needed to protect the 751 MEPs from possible terrorism.
A parliamentary source said private sector companies may be more susceptible to infiltration by individuals linked to jihadist groups.
A total 110 new drivers will be recruited for the in-house chauffeurs service, adding another €3.7m to the €7m already in the parliamentary administrative budget for MEP transportation.
Measures were also approved to improve the screening of drivers working as chauffeurs for the Parliament.
Currently, the Parliament's chauffeur service is provided by external companies. They employ a total of 65 drivers in Brussels and a further 85 in Strasbourg.
UKIP MEP and Security spokesman Mike Hookem was quick to respond to the allegations.
On Monday, he told this website, "Given we know that one of the Brussels bombers worked in the European Parliament as a cleaner it is very credible that a number of its chauffeurs, mainly drawn from an Arabic background, would have dangerous Islamist sympathies."
He added, "Brussels is the jihadist capital of Europe, as well as the main seat of the EU. Mass immigration, Schengen open borders, and a policy of non-integration all add into an explosive mix extremely detrimental to our security. It is one of the reasons why are safer outside the EU."