BEIRUT, Lebanon (AP) – An investigating magistrate began interrogating four pro-Syrian generals on Friday charged in the assassination of former Lebanese Prime Minister Rafik Hariri, Justice Ministry officials said.

Lebanon”s top prosecutor issued a preliminary criminal charge against the Lebanese generals late Thursday, just hours after they were accused by a top U.N. investigator of allegedly playing a role in planning the Feb. 14 bombing that killed Hariri and 20 others.

Prosecutor-General Said Mirza referred the four suspects to investigating magistrate Elias Eid for interrogation, after which their fate will be decided. They could either be released, remain in custody or face arrest warrants.

Brig. Gen. Mustafa Hamdan, commander of the Presidential Guards Brigade, was the first interrogated Friday after being brought from detention at police headquarters to the nearby Justice Ministry.

The other three suspects are: 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.

The three stepped down in April amid intense public criticism over their handling of the murder probe and claims of Syrian involvement in the killing.

The suspects led Lebanon”s security services at the time Hariri was killed, held close ties with Lebanon”s longtime powerbroker, Syria, and have been detained for questioning since Tuesday.

Hariri”s son and political successor praised the U.N. investigation, particularly the declaration that the four generals were allegedly involved in his father”s killing.

&#34It seems that the results achieved by the international investigation constitute essential steps towards uncovering the truth and the pursuit of justice,&#34 Saad Hariri said in a statement issued in Paris late Thursday.

U.N. chief investigator Detlev Mehlis said Thursday that more people were involved in Hariri”s assassination, but that no Syrian suspects had been identified yet. He said his 10-week investigation was, however, encountering &#34problems&#34 in getting Syria to cooperate. Syria had its army in Lebanon at the time of Hariri”s death and controlled political and security affairs here for most of the last 29 years.

Many Lebanese blamed Syria for Hariri”s killing, which sparked anti-Syrian protests and intensified international pressure on Damascus to withdraw its army, a move completed in April. Since then, anti-Syrian groups led by Saad Hariri have swept to power in parliamentary elections.

Syria and its then-allied Lebanese government have denied involvement in Hariri”s murder.

The slain premier”s son urged all parties to cooperate with the investigation, without naming Syria. &#34I repeat my demands that all factions, inside Lebanon or outside it, fully cooperate with the international probe,&#34 said Hariri, head of Lebanon”s largest parliamentary bloc.

While details of the investigation have been secret, local and Arab press have carried reports of alleged involvement of the generals in planning the attack and its subsequent cover-up.

But Samar Hajj, wife of one of the suspects, dismissed the accusations and denounced the campaign against her husband, particularly in the Hariri-owned media. &#34They (opponents) are confused and want to level accusations left and right,&#34 she told a call-in show on Lebanese Broadcasting Corporation.