Chief UN investigator Detlev Mehlis arrived in Damascus on Tuesday to question several Syrian officials on the assassination of former Lebanese Prime Minister Rafik Hariri.

Mehlis reached Syria through the border crossing of Jadeidet Yabous in a heavily-guarded convoy, an informed source told Xinhua.

According to the source, the chief UN investigator is expected to question Syrian Interior Minister Ghazi Kanaan, a former military intelligence chief in Lebanon, and his successor Rustom Ghazaleh who left along with Syrian troops in April.

Two of their key aides in Beirut, Mohammed Makhlouf and Jamaa Jamaa, may also be questioned.

Mehlis visited Syria on Sept. 12, during which the Syrian Foreign Ministry had agreed the procedures for his meetings with the Syrians officials, paving the way for the questioning this time.

Syrian President Bashar al-Assad has pledged full cooperation with the UN investigation team, saying Mehlis could question anyone.

Hariri was killed in a car bomb blast in Beirut on Feb. 14 and many Lebanese blamed Syria and its Lebanese allies for the killing, but Damascus has denied any role.

The assassination had sparked massive anti-Syrian protests and led to Syrian troops withdrawal from Lebanon in April after 39 years of military presence under growing pressure from the US and West countries as well as Lebanese opposition parties.

The UN-led investigation came to a breakthrough as Lebanon charged four pro-Syrian generals with the assassination earlier this month after Mehlis strongly recommended their arrest.

Source: Xinhua