Interior Minister Tsvetan Tsvetanov said two of the suspects in the July 2012 attack had been living in Lebanon for years one with a Canadian passport and the other with an Australian one. He said investigators had traced their activities back to their home countries.
"We have well-grounded reasons to suggest that the two were members of the militant wing of Hezbollah," Tsvetanov said.
A third suspect entered Bulgaria with them on June 28, he said, without giving details.
Lebanese Prime Minister Najib Mikati condemned the attack and said his country would cooperate fully.
Hezbollah, a Shiite militant group and political party in Lebanon that emerged in response to Israel's 1982 invasion, has been linked to attacks and kidnappings on Israeli and Jewish interests around the world.
The group has denied involvement in the Bulgaria bombing, and Hezbollah officials in Beirut declined comment Tuesday.
The bomb exploded as the Israeli tourists were on their way from the airport to their hotel in the Black Sea resort of Burgas. The blast also killed a Bulgarian bus driver and the suspected bomber, a tall and lanky pale-skinned man wearing a baseball cap and dressed like a tourist.
Although it was initially believed to be a suicide bombing, Europol Director Rob Wainwright told The Associated Press that investigators now believe the bomber never intended to die. He said a Europol expert who analyzed a fragment of a circuit board determined that the bomb was detonated remotely. He said investigators were still looking into who detonated it and how one of the suspected bombers was killed.
Bulgarian investigators found no links to Iran, which Israel had accused of playing a role in the attack.
The findings increased pressure on Europe to declare Hezbollah a terrorist organization.
Israeli Prime Minister Benjamin Netanyahu called the investigation "further corroboration of what we have already known, that Hezbollah and its Iranian patrons are orchestrating a worldwide campaign of terror that is spanning countries and continents."
"We hope the Europeans learn the proper conclusions from this about the true character of Hezbollah," Netanyahu said.
The Obama administration called on Europe to take "proactive action" to disrupt Hezbollah.
In strongly worded statements, Secretary of State John Kerry and White House counterterrorism adviser John Brennan said the Europeans, along with other countries that have balked at imposing sanctions on Hezbollah, must act to prevent additional attacks.