Arne Feuring, president of police in Frankfurt an der Oder, told the news agency DAPD that seven of the wounded were in critical condition, while another 27 suffered injuries that were not life-threatening.
Polish Prime Minister Donald Tusk and Health Minister Ewa Kopacz arrived in Berlin later Sunday to view the crash site and visit the injured, who were being treated in several Berlin hospitals.
Ahead of his arrival, Chancellor Angela Merkel called Tusk to express her sympathy and vow that German doctors and officials would do their utmost to help heal the wounded.
"This accident affects not only our Polish friends, but us as well," German Foreign Minister Guido Westerwelle said in a statement. "Our deepest sympathy and our thoughts are with the friends and family of the victims in their dark hour."
Feuring said authorities believe the bus, carrying 49 Poles on their way home from a vacation in Spain, crashed into a car that was merging on to the highway and then slammed into a pylon of an overpass.
The merging car's 37-year-old driver was among the injured, he said. An investigation into the accident has been launched.
German officials said they were organizing an information point for Polish relatives of the victims.