Over 70 people had to be rescued from the Mestre Simão passenger ferry after it ran aground on rocks in bad weather as it approached Madalena do Pico in the Azores on Saturday.
No-one was hurt, and it is not clear if any foreign holidaymakers were involved.
The issue on Sunday was to try and stem the leak of fuel into the waters.
Said the Azorean president Vasco Cordeiro, weather conditions were helping and giving authorities the window of opportunity they needed to evaluate the boat’s condition and “understand the true dimension of her physical state”.
It is possible that Mestre Simão ran aground due to a technical fault, though Saturday’s strong waves are thought to have contributed.
An inquiry to establish the causes of the accident is underway.