The spokeswoman, Kinga Wustinger, said the relatives were due to arrive on two buses in the town of Königs Wusterhausen on Berlin's southeastern rim where police set up an information centre after Sunday's accident.
"The police are still identifying bodies so some of them do not know whether their loved ones are alive or dead," Wustinger told AFP. "Some of the victims at hospital are unconscious and thus cannot be spoken to."
Six people injured in the crash on a rain-soaked motorway have left hospital, police said. Thirty-two were still in treatment at 15 clinics in the region, and eight were reportedly still fighting for their lives.
"Of the 20 people who were slightly injured, six have been released and returned home on board a bus supplied by the embassy," said police spokeswoman Bettina Schramm.
Polish Prime Minister Donald Tusk arrived at the scene Sunday evening to speak with survivors.
Chancellor Angela Merkel offered her condolences during a meeting at the Polish embassy and promised that Germany would do everything it could to save the lives of the injured, a government spokesman said.
"Our thoughts are with the families and the Polish people," Merkel told reporters.
Tusk returned to Warsaw late Sunday, Wustinger said.
Official buildings in the Brandenburg region surrounding Berlin lowered their flags to half-mast in honour of the victims, the state interior ministry said.
A car collided with the Polish tourist coach carrying 47 passengers and two drivers returning from Spain, causing the bus to lose control and crash into bridge pillars in the deadliest traffic accident in Germany this year.
The trip was organised by the forest service of the town of Zlocieniec in northwestern Poland, the TVN24 Polish television station reported.
The car, a Mercedes, was driven by a 37-year-old woman who was seriously injured in the accident, according to media reports.
A police spokesman said that the car spun out of control at around 10:00 am as it joined the A10 motorway from the A113 not far from Berlin's Schoenefeld airport, south of the capital.
After colliding with the coach, the car ended up in a drainage ditch under the bridge.
It had been raining most of the night and morning, and investigators have opened an inquiry into the cause of the crash, examining whether it was weather-related.
Germany's busy A10 motorway was closed for several hours as emergency services, assisted by half a dozen helicopters, treated the injured, cleared away the debris and began their investigation.
Pieces of metal and glass littered the ground the grey coach, which had its windshield and windows along one side shattered. Three people were reportedly flung from the bus upon impact and their bodies were recovered from the motorway.