More than 100 relatives, colleagues and supporters gathered at a Lisbon church on Friday to mourn the deaths of five Portuguese nationals who died in this week's streetcar crash in the capital.

Four of the victims worked at the same Catholic charity, Santa Casa de Misericordia.

Stricken mourners, many dressed in black and fighting back tears under a bright blue sky attended a Mass in Lisbon's Church of Saint Roch.

Among the mourners was Gonçalo de Oliveira, an actor from Lisbon, who had adopted three children through Santa Casa de Misericordia with the help of one of the victims, Ana Lopes.

Adopting children was a lifelong dream for him, Oliveira said, and through the decade-long process, he crossed paths with Lopes at family reunions and events.

He said many of the Santa Casa di Misericordia workers who died took the streetcar to work so often, it felt like they were already at work.

His family members also regularly ride the cars.

Officials have not yet said what caused Wednesday's crash on the Elevador da Gloria, which killed 16 people in total.

The foreign nationals among the dead included three British citizens, two Canadians, two South Koreans, one American, one French, one Swiss and one Ukrainian, police said in a statement.

AP video shot by Herman Munoz