An employee of the domestic German intelligence agency who had been hired to observe Islamists in Germany is facing charges of making Islamist statements and illegally sharing agency files.

The 51-year-old suspect allegedly planned to explode a bomb at the central office of the Bundesverfassungsschutz (BfV) in Cologne, Die Welt reported. The man reportedly was caught by an agency informant.

"The man is accused of making Islamist statements on the internet using a false name and of revealing internal agency material in internet chatrooms," a BfV spokesman said, adding, however, there was no “concrete” evidence of danger.

Der Spiegel reported the agency has been investigating the suspect for about four weeks. The report said the man’s family was unaware he had converted to Islam.

The BfV estimates about 40,000 Islamists are in Germany, including 9,200 Salafists, the ultra-conservative sect, Reuters reported.

German authorities have ramped up surveillance of potential terror groups and individuals following two attacks for which the Islamic State group claimed responsibility that left 20 people injured during the summer. Germany’s spy agency, the Bundesnachrichtendienst (BND), and BfV are ramping up efforts to monitor internet and phone messaging services, saying the “security of Germany and its citizens can no longer be taken for granted.”

The BND also warned ISIS trained terrorists to merge with asylum seekers fleeing to Europe, teaching them how to answer questions during border interrogations to pass scrutiny, Deutsche Welle reported. Germany accepted nearly 1 million refugees fleeing Syria, Iraq and elsewhere in the last year.

Earlier this month German prosecutors said they had broken an international Islamist terrorist network with the arrest of five men allegedly involved in smuggling people out of Germany to ISIS in Syria.

BfV said half of the 274 extremists who have returned to Germany from Syria and Iraq still support the radical cause, Die Welt reported. A confidential paper prepared by the BfV, Federal Criminal Police and the Hessian Information and Competence Centre against Extremism only 9 percent of returning radicals are disillusioned.

ISIS has been urging its supporters in Europe not to travel to its self-declared caliphate and instead conduct terrorist actions in their homelands.