Captain Dario Pinto Moreira, who is in charge of the port at nearby Cascais, told Portuguese news channel CMTV that the Poles slipped while trying to take a photograph of themselves.
This Portuguese website claims the couple had lived in Portugal for five years and were on holiday.
According to the Telegraph, the couple crossed a barrier close to the cliff edge: "Weather conditions forced rescue workers to abandon attempts to recover the bodies on Saturday night, but the couple were eventually found on Sunday. The couple's children, aged 5 and 6, are now in the care of Polish diplomats and are seeing psychologists."