I forget where I read it but the ship apparently stopped at the Canaries and St Nazaire. Unlikely that they boarded at St Nazaire as the French authorities were reported to have refused to let them off there.I understand that there are now reports that she made not one but two port stops en route from Lagos.
Allegedly Ste Nazaire in France.
I think it is highly probable the non-paying pax got onboard there.
What the truth is, is anyone's guess.