Seven people fleeing Afghanistan have been red-flagged by security services after arriving in Germany from Kabul.
Three of the seven were found to be carrying false documents, German Interior Minister Horst Seehofer said.
Another four had previously been deported from Germany to Afghanistan.
“We are talking about serious crimes,” Mr Seehofer said.
It followed a similar case in Britain in which a person on a no-fly list was flown out of Kabul, although authorities said they were no longer a threat.
Afghans looking to leave were processed in the chaotic surroundings of the airport in Kabul after the Taliban took control of the city.
The German military flew more than 5,000 people out of Afghanistan during the two-week Nato airlift. Ministers have promised to keep the door open for Afghan personnel who were left behind.
But Mr Seehofer wants to step up the deployment of federal police to prevent an uncontrolled refugee surge at Germany’s borders.
Nine federal police officers were sent to Kabul to help the Nato evacuation efforts.
“If necessary, we will tighten the control measures at our borders,” Mr Seehofer told the newspaper Bild am Sonntag.
One of the seven Afghans was reported to be in custody. Two others were being dealt with by police at the airport. The status of the others was unclear.
Germany had hoped to continue deportations to Afghanistan after the Nato withdrawal, but they were called off days before the fall of Kabul.
Europe now wants to help Afghanistan’s neighbours to manage refugees and prevent a surge at EU borders.
EU foreign policy chief Josep Borrell said in an interview published on Monday that Afghanistan's neighbours needed financial support from Brussels,
“Afghans fleeing the country are not going to reach Rome, but maybe Tashkent” in Uzbekistan, he told Italian newspaper Corriere della Sera.
“The absorption capacity of Europe has its limits and nothing can be done without strong co-operation.”