A police spokesperson told Bild am Sonntag that the arrests signified a "great success for the prosecution and investigators."
One suspect, a 20-year-old man, presented himself to police after arriving from Istanbul before noon on Saturday. Eight hours later, the final suspect was arrested on the airport tarmac after the 19-year-old returned from Beirut, according to Bild am Sonntag's report.
The location of the €242,000 stolen during the high-stakes poker game at Berlin's Grand Hyatt Hotel is still unclear, but there is now speculation that the four robbers did not plan the heist themselves, according to a report published Sunday by the Berliner Morgenpost.
The newspaper reported that an Arab family known to police masterminded the crime. Two members of the family reportedly stayed at the Grand Hyatt hotel shortly before the heist and were recorded on surveillance footage, though police refused to comment.
A rival criminal group allegedly provided police with tips on the robbers' identities.
The investigation gained momentum last Monday, after a 21-year-old German turned himself in to police and provided the names of his accomplices. He told police he would return his share of the stolen money.
Two days later, a second suspect was arrested without resistance during a routine security check.
The arrests conclude a sweeping international search effort to track the suspects with names and photos. Police chief Dieter Glietsch said he was certain the four thieves would be arrested early on, but a full week passed before investigators achieved key breaks in the case.