A Polish national and three African men were arrested after they were stopped at the German-Austrian border in a car that contained weapons and materials to build explosive devices, a police spokesman said Friday.
A Polish man, 39, a Guinean man aged 20 and two men from the Ivory Coast aged 29 and 37 were stopped during routine border controls in the Bavarian district of Kiefersfelden and three pipes, explosive material and several ignition devices were found in their car.
Police also found several knives and a narcotic substance in the car, which was stopped at around 10:30 pm (2030 GMT) on Thursday.
The motorway was cordoned off while explosives experts examined the car in an operation that lasted more than seven hours.
Police concluded that though the materials could have been used to create pipe bombs, there was no immediate explosion hazard.
Authorities said they are investigating whether the Polish man was trying to bring the African men across the border illegally.
Germany took in 1.1 million migrants in 2015, partly due to Chancellor Angela Merkel's decision last September to effectively suspend vetting of Syrian refugees.
Though the country's borders remain open, border controls were stepped up earlier this year as public opinion began to turn against Merkel's open-door refugee policy.
Federal police hailed the discovery as a success, with a spokeswoman saying: "You can see that the (increased) border controls are paying off."