ROME, Sept 13 (Reuters) - The grandfather of a boy who was the only survivor of a cable car disaster in Italy has been placed under investigation for allegedly kidnapping the child and taking him to Israel, a legal source said on Monday. Six-year-old Eitan Biran"s parents, younger brother and 11 other people all died in the crash in northern Italy in May. read more The boy moved in with his paternal aunt in northern Italy, and his grandfather, Shmuel Peleg, picked him up on Saturday for a pre-planned family visit, the aunt told reporters. However, the pair did not return and Italian media reported that they had driven across the nearby border to Switzerland and were flown by a private jet to Tel Aviv. "The maternal grandfather arrived in the morning as planned, for a day of leisure ... it was a normal visiting day. But Eitan did not come home," Aya Biran Nirko, the aunt who was granted the boy"s custody last June, told reporters. Peleg"s lawyers acknowledged in a statement that he had taken the boy to Israel. They said Peleg had "acted on impulse" because he was worried about his grandson"s health and after being excluded from legal proceedings related to the boy"s custody. A legal source said prosecutors in the northern Italian city of Pavia have opened an investigation into kidnapping. The prosecutors" office declined to comment. Israeli media reported that Eitan"s maternal aunt Gali Peleg, who filed for adoption last August claiming that the boy was being held hostage, had denied committing any crime. "We did not kidnap him. We brought him home ... I am only speaking to clarify that we have acted for the good of Eitan," she was quoted as telling Israel"s 103 FM radio station. Magistrates are still investigating why the cable car, which connected the northern town of Stresa, on the shores of Lake Maggiore, to the nearby Mottarone mountain, plunged to the ground.