The German interior ministry says recent IT disruptions at German airports are not believed to be linked to hacking.
"To date, there are no indications of a hacker attack or any other IT security incident," a spokesman in Berlin said.
Instead, the ministry said the cause of Friday's delays was disruptions to an information system operated by the Federal Criminal Police Office (BKA).
This mainly affected travellers entering from and leaving to countries outside the visa-free Schengen Area.
In some cases passport controls had to be carried out manually, with long waiting times reported.
The outage was largely rectified by Friday evening.
The fault has been localised "in the IT network hardware" and a full resolution to the issue is expected to take a few more days, the spokesman explained.
"The BKA is working at full speed with its partner authorities to restore normal operations and find the causes," he said.