(CNN) -- Swiss police said Monday there have been no sightings of 6-year-old twin girls since they were abducted by their father more than a week ago.
The search for Alessia and Livia Schepp has since stretched to three countries -- Switzerland, France, and Italy -- after the father was found dead in Bari, Italy, on Thursday, police said.
Matthias Schepp, 43, committed suicide Thursday night on a railway in Cerignola, Italy, about 60 miles west of Bari, a spokesman for the Swiss police said. When police found the body, there was no sign of the girls.
Police discovered Schepp had bought ferry tickets for himself and his two daughters and validated them at the French port of Marseilles, intending to go to the Corsican port of Propriano, but police said it's unclear if they ever boarded the boat.
Authorities have dubbed their search Operation Gemelle, which means "twins" in Italian.
Interpol issued an international Yellow Notice missing persons alert for the girls Saturday. Such notices are distributed to police in Interpol's 188 member countries to help find missing people, especially children.
The girls were last seen January 30 when their father abducted them from their home in St. Sulpice, near Lausanne in western Switzerland, police said.
He took the girls following personal problems at home, according to the state police in Vaud, which covers the area of St. Sulpice.
Swiss police have since carried out three searches at the St. Sulpice home and investigated 60 other homes in the neighborhood, Vaud police said.
They have also searched the father's four boats at the ports of Morges and Vidy as well as other ports in the region. Police have contacted all service stations between St. Sulpice and the Swiss city of Geneva, monitored all customs posts in the Geneva region and hired a helicopter to search the lake near St. Sulpice.
Both girls are about 3 feet, 9 inches tall and have blond hair, Interpol said. When they were taken, Livia was wearing a green T-shift, jeans, a violet ski jacket and Adidas sneakers. Alessia was wearing a T-shirt with red and white stripes, jeans, a brown jacket and black shoes.
The headmaster of the girls' school in St. Sulpice visited each class Monday to inform the students and teachers of the situation, the Vaud police said. Psychological support is being offered at the school.
CNN's Saskya Vandoorne in Paris, France, contributed to this report.