Chief UN investigator Detlev Mehlis wants to question the former security chiefs, who are pro-Syria, the Lebanese officials said on Tuesday, speaking on on condition of anonymity.
The detainees were: Maj. Gen. Jamil Sayyed, the former chief of General Security; Maj. Gen. Ali Hajj, the former director general of the Internal Security Forces; and Brig. Gen. Raymond Azar, the former director general of military intelligence.
They have previously been questioned by chief investigator Mehlis, a German prosecutor.
Mehlis also asked for former legislator Nasser Qandil, a staunch supporter of Syria, to be detained for questioning, the officials said.
Legislator in Syria
But when police went to Qandil’s house in Beirut, he was not there and his wife said he was in Syria, the officials said.
A fifth person, Brig. Gen, Mustafa Hamdan, the pro-Syrian head of Lebanon’s Presidential Guards, was told he must come to Mehlis’s office for questioning, the officials said. Hamdan turned himself in soon after.
Hamdan has previously been questioned by Mehlis.
A UN team is probing al-Hariri’s
Al-Hariri and 20 others were killed in a massive bombing that targeted his motorcade in a Beirut street on 14 February.
Mehlis, is expected to report his findings to the Security Council in the next few weeks.
The killing of al-Hariri, which many in Lebanon blamed on Syria, brought mass anti-Syrian demonstrations in Beirut.
Damascus denied its involvement but bowed to world pressure and pulled out its 14,000 troops from the country in April.
Syrian President Bashar al-Assad said in an interview published on Sunday that Damascus would fully cooperate in the al-Hariri murder investigation after Mehlis criticised Syria of not cooperating with the inquiry.
The three arrested former officers were in their posts when al-Hariri was killed. They were blamed for negligence and a role in the attempted cover-up of the murder.
Sayyed, the former head of the most powerful pro-Syrian security organs, resigned one day before Syria ended its military presence in Lebanon in April.