Justice Minister Heiko Maas called for a "thorough" probe into Germany's Federal Criminal Police Office (BKA) on Wednesday following the release of a report that made "serious allegations" against the agency over its data-storing practices.

Maas also urged the officials to narrow their scope on data collection.

"Unnecessary data storage makes us less safe," he said in Berlin.

According to experts cited by the ARD, the BKA illegally archived trivial, outdated and "evidently false" information on alleged wrongdoings of 32 reporters who were subsequently blacklisted from the G20 summit in June.

Additionally, the federal police use similarly questionable methods to keep tabs on thousands of ordinary citizens, ARD claims.

Many of those entries allegedly violate German law, which requires authorities to provide cause that individuals would continue to commit similar criminal acts in the future.

Reporter blamed for a bomb blast

According to the report, the BKA maintains a database on drug crime which covers some 473,000 people and contains millions of pieces of data. A large majority of those citizens were flagged after the police linked them with a small amount of cannabis. Over half of all instances noted in the base are now over 10 years old.

One of the banned reporters, Björn Kietzmann, was flagged for "causing an explosive blast" at a protest he was covering in 2011. The data entry remained on record, even though prosecutors had dropped the allegation after the testimony of four of his colleagues exonerated Kietzmann.

Kietzmann and over 30 other reporters had their accreditation revoked on short notice ahead of the G20 summit in Hamburg, with authorities citing security concerns.

Nine of them subsequently filed suit against Germany's Federal Press Office.

No 'pattern' to be fixed

Commenting on the report on Wednesday, the German Interior Ministry acknowledged that four out of the 32 reporters were wrongly blacklisted. However, none of these mistakes are based on the information provided by the BKA, officials said. The authorities relied instead on information provided by state police departments and intelligence agencies.

Another case might have also been incorrect, officials said.

The ministry acknowledged there was need for improvement when it comes to "quality of data." However, they said there was no "specific pattern" of mistakes to be fixed. The process of improvement has already started and it will last for a long time, according to the officials.

The German Federation of Journalists (DJV) urged politicians to act.

"It's a bottomless pit of data misuse," DJV chairman Frank Überall said of the ARD report. "When journalists are being criminalized, intentionally or through negligence, politicians must not stay silent."

dj/kms (AFP, dpa, EPD)