NEW YORK (EJP)---Israel has evidence that a spike in telephone calls took place between Lebanon and the Bulgarian city of Burgas in the two months before the July 18  bombing of a bus that killed six people, including five Israeli tourists, the New York Times reported Thursday.

The report quoted an Israeli official saying that, according to an investigation, the number of phone calls made between Lebanon and Burgas in the two months leading up to the attack was unusually high. These phone calls further increased in number in the three days leading up to the attack.

The official said that the volume of the calls increased in the three days before the bombing at the Burgas Airport.

"We know the sources in Lebanon," the official was quoted as saying. The official added that the identities of those on the Bulgaria end of the calls have not been identified.

"They shouldn’t know that we know the numbers in Lebanon," the official said.

Israel has said that Iran and Hezbollah orchestrated the Burgas attack.

American and Bulgarian officials support Israel's assessment off the record, but won't say so publicly, the New York Times report said.