SOFIA, Bulgaria — Nearly two weeks after the bombing of a busload of Israeli tourists, Bulgarian investigators said they had yet to identify the bomber, and did not publicly indicate who they believed was behind the attack. But if the trail remains murky, the impact of the disaster on this small Balkan nation is clear: It has jeopardized its strong ties with both Israel and the Arab countries of the Middle East.

Bulgarian officials have been notably reluctant to join Prime Minister Benjamin Netanyahu of Israel in publicly pinning blame for the attack, which killed five Israelis and a Bulgarian bus driver, on Hezbollah and Iran, a view privately shared by American officials. Instead, the government has tried to contain details about the investigation, hoping to avoid mistakes in a situation with global political and security implications, as evidence grows of a shadow war between Israel on one side and Iran and Hezbollah on the other.

“For small Bulgaria to come out and openly name Hezbollah in such a way is as good as entering a minefield,” said Vladimir Shopov, a political scientist at the New Bulgarian University in Sofia. “There would have to be absolute certainty almost. You’d have to be really, really confident that your convincing evidence could stand up before all the other members of the E.U.”

A member of the Bulgarian security establishment, speaking on the condition of anonymity because the investigation is continuing, said that there was a “clear direction that points to Hezbollah” in the pattern and evidence of the attack, but that it would probably be some time before any official determination was made.