Switzerland's Massoel Shipping has confirmed that contact has now been made with those who are holding hostage 12 crew from its bulker Glarus.
It is understood that all the seafarers are together and all are well and unharmed, it added.
The 47,000-dwt ship (built 2001) was attacked off Bonny Island, Nigeria, on Saturday, and 12 of 19 crew kidnapped.
The vessel is now safely alongside at Port Harcourt with the remaining seven crew members on board.
"Families are being kept in close touch with developments, the first and absolute priority being the safe release of the hostages," it added.
"Massoel will not be making any further comments on operational issues as this could prejudice the safety of those being held."
Earlier, Nigerian media reported that a search and rescue (SAR) operation had begun.
The Nigerian Maritime Academy said the mission has been launched for the crew from the Philippines, Slovenia, Ukraine, Romania, Croatia and Bosnia who were taken from the vessel, according to the Punch daily.
Maritime authority NIMASA's director general Dakuku Peterside said the agency was working closely with the navy's Forward Operation Base and its Falcon Eye surveillance system along with other relevant security agencies to ensure the release of the crew members.
“The issue of piracy in the Gulf of Guinea is a challenge we acknowledge and we are determined to tackle it head-on," he said.
"We will continue to collaborate with the Nigerian navy and other relevant partners to ensure we bring it to a halt. Zero tolerance to piracy and all forms of illegalities on our nation’s waterways is our goal.”
Navy begins investigation
The Nigerian navy said it had begun an investigation that will lead to the rescue of the seafarers.
A navy official in Port Harcourt told Punch that it had received information on the kidnapping.
The vessel was carrying wheat between Lagos and Port Harcourt when it was boarded.
