Three days after a deadly blast in a popular vacation spot killed five Israelis and a Bulgarian, investigators in Bulgaria and in several other countries continued their investigations into the crime as they tried to close in on the identity of the bomber.

Israel’s Mossad and Shin Bet intelligence agencies had teams on the ground at the Black Sea resort of Burgas helping with the probe.

Bulgarian Interior Minister Tsvetan Tsvetanov said Friday evening that the bomb had been carried in the backpack of a man caught on security cameras at Burgas’s Sarafovo Airport shortly before the blast there.

Tsvetanov said the bomb had detonated in the luggage compartment of the bus carrying Israelis from the terminal to their hotels on Wednesday afternoon. The bomber was believed to have been about 36 years old and had been in the country between four to seven days, he said.

He later said in an interview with state TV that the blast was caused by 3 kilograms of TNT powder.

Bulgarian prosecutors said the attacker had short hair, not the long hair seen in the security video footage captured of him at the airport where the attack took place Wednesday afternoon. A witness said the man appeared to be wearing a wig.

The same man, according to eyewitnesses quoted on Israel’s Channel 2 news, had been seen speaking to tourists at local beaches in the days before the attack.

According to one eyewitness report, the man struck up a conversation with tourists from Holland, and told them that his mother was Dutch and his father was Iranian.

An analyst on Israel’s Channel 2 suggested that the bombing may not have been a deliberate suicide bombing, but that the device may have detonated prematurely, killing the attacker.

Bulgarian authorities on Friday released an artist’s sketch of a man believed to have helped the bomber.

Israeli and American officials have blamed the Iran-backed Lebanese terrorist group Hezbollah for Wednesday’s bombing, which killed five vacationing Israelis, along with a Bulgarian bus driver and the attacker.

Devastated mourners grasped at dirt atop fresh graves and screamed in agony Friday as they buried the five Israeli victims of the blast.

In a TV interviews Friday, Defense Minister Ehud Barak said he was certain who carried it out.

“Hezbollah is behind the attack, it was part of a series of attacks,” he told Israel’s Channel 2 TV. “We know that Iran is behind it all. What we don’t know is who the actual man is.”

Deputy Prime Minister Moshe Ya’alon expressed similar sentiments on Friday, warning that Israel would respond at the right time and place to the attack, which he said was perpetrated by Iran.

Though Iranian President Mahmoud Ahmadinejad gloated over the attack on Thursday, Iran denied responsibility for the attack, which threatened to further escalate a shadow war between the two countries over allegations that Tehran is trying to build nuclear weapons.

Security camera footage from before the attack showed the suspected bomber wandering in and out of the terminal, wearing a baseball cap over long hair, a T-shirt and plaid shorts, with a bulky backpack.

Bulgarian prosecutors said the man tried to rent a car in the days before the bombing but was turned down because his ID appeared suspicious. Authorities have examined his fingerprints, his DNA and his fake Michigan driver’s license.

They also said the man actually had short hair. It was not clear if he was wearing a wig, or if he had a haircut after the airport footage was taken.

Afrodita Petrova, the owner of the car rental company, told Bulgarian National TV that the suspect had short dark hair when visiting the office. She said he was the same person from the video camera footage and appeared to be wearing a wig.

“He spoke English with an Arab accent,” she said.

Tsvetanov said the investigation had ruled out that the bomber was a Bulgarian citizen, but did not say how authorities know that. He said the investigation had also ruled out that the bomber was Mehdi Ghezali, a Swedish citizen and former Guantanamo detainee whom authorities had previously fingered as the bomber.

“Now we are focused on finding out the identity of the suicide bomber and his possible whereabouts ahead of the blast,” Tsvetanov said.

Police and prosecutors refused to give any more information, saying it would compromise the ongoing investigation.

US President Barack Obama called Bulgarian Prime Minister Boyko Borisov Friday to offer his condolences and continued support in the investigations into the terror attack.

Israel has attributed a series of attacks on its citizens around the world in recent months to Iran and its Islamic terror proxies.

Hezbollah has not commented on the attack.

Iranian Foreign Ministry spokesman Ramin Mehmanparast called the accusation “baseless.”

A US official told The Associated Press on Thursday night that Hezbollah was believed to be behind the attack. The official spoke on condition of anonymity to discuss a sensitive intelligence issue.

However, Pentagon press secretary George Little said Friday the US government has not established with certainty who was behind the attack.

“The attack does bear some of the hallmarks of Hezbollah, but we are not in a position to make any final determination,” Little said. He declined to say what aspect of the attack resembled the methods or other features of Hezbollah.

Israel has officially issued a complaint with the UN Security Council, accusing Iran of responsibility for the attack. Israeli representative Haim Waxman wrote the Security Council president that the attack in Bulgaria was part of an international terrorist campaign against Israelis and Jews worldwide, led by Iran and Hezbollah.