Michal Czerepaniak, head of Polaris Maritime Services in Szczecin, said on Polish radio today that the five were "safe and sound." He gave no further details.
Poland's Foreign Ministry could not immediately confirm the information.
Armed attackers abducted the captain, three officers and a seaman from the MV Szafir cargo ship in Nigerian waters on Thursday.
The remaining 11 crew members barricaded themselves inside the ship and were left unharmed.
The ship was being brought to a naval port in Nigeria while Nigerian and Polish authorities continued efforts to have the abducted crewmen released.