- Investigators in Bulgaria are seeking clues to the identity of a suicide bomber
- The man was a foreigner who entered Bulgaria with false papers, the interior minister says
- The suspect had been in Bulgaria for at least four days, he says
- Israel has accused Iran and Hezbollah in the attack, a claim denied by Iran
Burgas, Bulgaria (CNN) -- Investigators in Bulgaria are working around the clock to identify the man suspected of killing five Israeli tourists and a bus driver in an airport suicide bombing, the country's interior minister told reporters Friday.
Bulgarian Interior Minister Tsvetan Tsvetanov said police were trying to piece together the movements of the suspect, who was carrying a fake Michigan driver's license.
Investigators are also working to analyze the bomb, believed to have been in a backpack placed on the bus in a parking lot outside Burgas International Airport on Wednesday, Tsvetanov said.
Israel has said it suspects Iran or an Islamist militant group such as Hezbollah is behind the attack, a claim which has added to escalating tensions between Israel and Tehran. Iran, which has condemned the attack, has rejected Israel's claims.
"At the moment, we are focused on finding the identity of the suicide bomber, and of course from the moment of the blast every single minute and every single hour of his being on the territory of Bulgaria," Tsvetanov said in a news conference broadcast on Bulgarian National TV.
The suspect was a foreigner who entered the country with fake identification documents and had been in Bulgaria for at least four days, he said.
Experts believe the attack was planned for the precise moment and place that it happened, he said, and they are certain from DNA analysis of body parts found at the scene that the attack was carried out by a suicide bomber.
But Tsvetanov said he was not excluding the hypothesis that a second person might have been involved.
Bulgarian authorities are working with their Israeli counterparts and international organizations like Interpol and Europol to try to identify the suspect, Tsvetanov said.
Authorities still don't know where the suicide bomber came from, where he stayed or what he did, Tsvetanov said.
A witness has said the suspected bomber tried to rent a car from him but didn't have a proper driver's license, so was turned away, the minister said. FBI officials have said the Michigan license the man had was a fake.
Security footage aired by Bulgarian National TV shows the suspect, who is white with long hair and wearing khaki shorts, a baseball cap and sneakers, looking relaxed as he walks among other travelers, carrying a backpack and a smaller bag.
Tsvetanov said local media reports that the suspect had a link to the Guantanamo Bay detention camp were incorrect. He also dismissed as speculation local newspaper reports that the airport had received a warning about an hour before the attack.
The bombing also left more than 30 Israeli tourists injured, some seriously. Israel's military flew 33 of the injured back to Tel Aviv on Thursday. They were taken to Israeli hospitals for treatment.
The airport bus targeted by the attacker was to have taken about 47 passengers to a beach resort.
Bulgaria, whose affordable Black Sea resorts are a popular destination for Israelis, has not speculated on who may have been responsible for the attack. Bulgaria received nearly 8.4 million visitors in 2010, the last year for which U.N. World Tourism Organization figures are available. The vast majority of the country's visitors that year, more than 8 million, came from Europe. About 25,000 visitors came from the Middle East.
Bulgarian officials have sought to reassure those worried by what is an unusual attack in the nation, saying security has been boosted wherever needed.
Burgas airport has now reopened and is functioning normally, Tsvetanov said, but access is restricted to passengers.
In a televised statement Thursday, Israeli Prime Minister Benjamin Netanyahu said the attack was "perpetrated by Hezbollah, Iran's leading terrorist proxy," as part of a global campaign that has reached a dozen countries on five continents.
But he offered no evidence. Israel's U.S. Embassy said Wednesday that it had no proof that Iran was the instigator of the attack.
Netanyahu said Hezbollah and Iran have been trying to foment terrorism in countries that include Kenya, India and Cyprus, as well as in the United States, where an Iranian is accused of trying to kill the Saudi diplomat.
"We will continue to fight against the terrorists and exact a heavy price from those that support them," Netanyahu said.
Iran's Foreign Ministry spokesman, Ramin Mehmanparast, said Israel was engaging in "baseless accusations against other countries in order to distract the attention of the international community from its terrorist activities being carried out throughout the world," according to a statement from the state-run IRNA news agency.
The Iranian Embassy in the Bulgarian capital of Sofia said earlier that Israeli suggestions that Tehran was involved in the attack were "unsubstantiated" and that the assertion was politically motivated.
CNN's Boriana Milanova, Atika Shubert and Laura Perez Maestro contributed to this report.
