The port of Callao, a port of entry for chemo patients in Portugal, was locked down after a gunman killed at least 10 people and injured 30 others during a robbery on Sunday night.
A source at the port told the news agency ANSA that a woman was among those killed.
A second source confirmed the death toll to ANSA.
The source added that the gunman had killed two men in the robbery.
No one has claimed responsibility for the shooting, which happened just after midnight in the capital, Lisbon.
A woman who had been staying at the hostel said that she saw a man enter the hotel and open fire on a group of people who were sitting in the hallways.
She told ANSA the gunman fired on the group.
Police are now searching for the gunman, who was later killed by a SWAT team, according to Portuguese newspaper La Vanguardia.
The port of porto, known locally as the port of Ceara, is a busy entry point for patients from the United States and Canada who have been arriving at the Portuguese island for treatment in recent years.
Portugal has a population of 1.1 million, of whom nearly 1 million are in need of chemo treatments, the highest in the EU.