LISBON, March 25-- Portuguese Prime Minister Pedro Passos Coelho conveyed his condolences on Wednesday to his Spanish counterpart Mariano Rajoy, German Chancellor Angela Merkel and the families of the victims of a plane crash on Tuesday in the French Alps.

"During these tragic times, I would like to transmit to Germany and to the family of the victims my most sincere condolences," Passos Coelho said in a letter sent to Angela Merkel.

In his letter to Mariano Rajoy, Passos Coelho said this was a time of "pain and sadness" and sent the Spanish prime minister a "strong hug of solidarity."

"In this period of pain and sadness, I want to convey, in the name of the Portuguese government, my most profound solidarity with the victims of the crash," Passos Coelho wrote.

An airbus operated by Lufthansa's Germanwings carrier flying from Barcelona to Duesseldorf and carrying 150 people, crashed in a remote area in the French Alps on Tuesday, killing all 144 passengers and six crew members on board.

Germanwings has estimated that 67 Germans were on board, and the Spanish government has said that around 45 names were Spanish, however the final result of the victim's nationalities has not been concluded.

The cause of the accident remains unknown and French aviation investigators are examining one of the black boxes (voice recorders) from the plane which was found and sent to the French air investigation bureau on Wednesday.