Police said Tuesday they were "amazed" to find an SUV at the Swiss-German border crammed with 23 members of the same family.

The seven-seater Seat Alhambra, carrying the members of an "extended family" on their way from Poland to the Swiss capital Bern, was stopped by a customs officer on Monday morning, according to German police.

The Swiss official was "certainly amazed" by his discovery at the border between the German town of Weil am Rhein and the city of Basel, police said in a statement.

The family, which included nine adults and 14 children, was briefly barred from entering Switzerland and the German authorities were "notified", added the statement.

However, once all paperwork was completed, the family was allowed to enter Switzerland, but "not all in the Seat Alhambra", police said.

The driver of the vehicle, a resident of Switzerland, could "expect to receive a fine" for carrying the passengers "completely unsecured" in his vehicle, German police said.