Evidence suggests both Syrian and Lebanese involvement in the murder of former Lebanese PM Rafik Hariri, a United Nations investigation has found.
The inquiry is not yet complete, and Secretary General Kofi Annan has given investigators more time to finish their work.
But in a preliminary report to the UN Security Council, German investigator Detlev Mehlis outlines his progress so far.
Here are some of the figures mentioned in the report, which followed months of interviews with hundreds of witnesses.
Lebanese Sheikh Ahmed Abdul Al
The report says Sheikh Ahmed Abdul Al, a leading figure in a Lebanese group with strong ties to Syria, has proved to be a significant figure in the inquiry.
His mobile telephone was found to have had key contacts with all the important figures in the inquiry, the report says.
"Indeed, it does not appear that any other figure is as linked to all the various aspects of this investigation as Abdel-Al," the report says.
The pro-Syrian Sunni Sheikh will be a key figure in any ongoing investigation, the report says.
The sheikh's group, al-Ahbash, has denied any involvement in the attack.
Emile Lahoud, president of Lebanon
The report says that Lebanon's Syrian-backed President, Emile Lahoud, received a mobile phone call shortly before Mr Hariri was killed from Mahmoud Abdel-Al, the brother of a key figure in the inquiry, Sheikh Ahmed Abdel-Al.
Mr Lahoud's office denies that such a call was received, and Mr Lahoud has previously denied any wrongdoing over Mr Hariri's death.
Asef Shawkat, head of Syrian military intelligence
One of the most powerful men in Syria, Mr Shawkat is married to the only daughter of the late president, Hafez al-Assad, and is thus the brother-in-law of the current president, Bashar al-Assad.
Asef Shawkat is accused over a video "confession"
A witness told the inquiry that Mr Shawkat forced Ahmed Abu Adass, an Islamic militant, to make a video claiming responsibility for the bombing that killed Mr Hariri - two weeks before the explosion.
The UN has found no evidence to link Abu Adass to the scene, and a witness has told the inquiry Abu Adass has since been killed in Syria.
The report says it seems likely that Abu Adass left his home on 16 January 2005 and was taken to Syria "voluntarily or not" where he has since disappeared.
Bashar al-Assad, president of Syria
The report details a meeting in Damascus between President Assad and Mr Hariri on 26 August 2004. The two men were deeply opposed over Syria's involvement in Lebanon, and over Syria's wish to extend Lebanese President Lahoud's mandate.
Bashar al-Assad did not give evidence to the UN
The UN report says the meeting "appeared to bring the conflict to a head".
Mr Hariri's son, Saad, and other witnesses said that President Assad personally threatened his father at the meeting. Syrian accounts describe the meeting as cordial and brief.
Overall, the report concludes that its inquiry has been impeded by lack of co-operation by the Syrian government.
The Syrian president did not testify before the UN investigation, and has denied involvement in the killing.
Faruq al-Shara, Syrian foreign minister
UN investigators said Mr Shara supplied false information to them in a letter about a meeting between Mr Hariri and Syrian President Bashar al-Assad.
The four accused Lebanese generals
Four Lebanese generals have been arrested for allegedly conspiring to commit Mr Hariri's murder. They are General Jameel al-Sayyed, General Ali al-Hajj, General Raymond Azar and General Musapha Hamdan.
Witnesses told the inquiry that Gen Sayyed co-operated closely with Gen Hamdan and General Azar in preparing the killing, and that Gen Hajj also knew of the crime in advance.
Gen Hamdan was said to have told one witness: "We are going to sent him on a trip, bye bye Hariri."
Gens Hamdan and Azar were specifically accused by a witness of providing logistical support and equipment in the murder plot.
All four deny any involvement in the plot or any foreknowledge of it.
Syrian General Rustom Ghazali
The former head of Syrian intelligence in Lebanon, Lt General Rustom Ghazali, is said by witnesses to have helped the four accused generals co-ordinate the attack.
The report also highlights a telephone conversation in which General Ghazali tells a Lebanese official that the Syrian president has told him: "Things cannot continue this way" - in a reference to the problems being posed for Syria by Mr Hariri.
Zuhir Ibn Mohamed Said Saddik
Zuhir Ibn Mohamed Said Saddik, described by other sources as a defected Syrian soldier, is named in the report as a witness who later became a suspect. He says the decision to kill Mr Hariri was taken in Syria by senior Lebanese and Syrian officers.
He says the initial planning meetings were held in his flat, and gave information about the vehicle and explosives used in the bombing.
The report says his statements cannot be verified, but the fact that he implicates himself gives him added credibility.
Late Syrian Interior Minister Ghazi Kanaan
The former interior minister - who was for decades Syria's
top man in Lebanon - was found dead in his office days before the report was completed.
A Syrian investigation concluded he had killed himself.
He was not named in the report.