At least seven tourists, including Israeli citizens, were killed Wednesday in a suicide bombing of a tour bus in Burgas, Bulgaria. The Israeli government accused Iran and Shiite movement Hezbollah of carrying out the attack, allegedly conducted by a man carrying a false U.S. identification card.
An autopsy report revealed the bomber was a white male, 20-30 years old.
Bulgarian police distributed a sketch of another suspect that resembles someone of Arab descent.
Bulgarian authorities revealed to ABC News that the bomber didn't act alone.
"The key question is from what country the bomber entered Bulgaria. At the moment we do not have an answer," one official was quoted as saying. "But what we know now is that he was not acting alone."
The Wall Street Journal, citing a person familiar with the investigation, said authorities weren't able to match the bomber's fingerprints with potential suspects. Investigators are working with Swedish forensic teams as Hezbollah has a strong presence in the country, the newspaper reported.
Iran denied suggestions it played a role in the bombing.
Notable deaths of 2014 [PHOTOS]