Lebanese officials say authorities have detained a wife and son of the Islamic State’s leader.
The two were detained 10 days ago using fake identification cards.
Both officials refused to give any details about the woman who is believed to be one of the wives of Abu Bakr al-Baghdadi, the group's reclusive leader.
The officials spoke on condition of anonymity in line with regulations.
Lebanon announced the arrests amid attempts to reach a prisoner-exchange deal between the country and ISIS and Al Qaeda's Nusra Front, who are holding more than 20 Lebanese soldiers.
On Monday night, the Nusra Front threatened to kill one of the soldiers it is holding captive.
The wife's arrest could be used as a bargaining chip for Lebanese authorities in their attempts to win the freedom of the troops.
A judicial official said the interrogation is being supervised by Lebanon's military prosecutor, Saqr Saqr. He added that a DNA test is underway to confirm that the child is the son of the detained woman.
The Lebanese daily As-Safir was the first to break the news, saying they were detained near a border crossing point with Syria. It added that the arrest was made in "coordination with foreign intelligence agencies."
There is not much known about al-Baghdadi's personal life. It is unclear how many wives and children he has.
Al-Baghdadi's first wife is believed to be Iraqi citizen Saja al-Dulaimi, who was reportedly held by Syrian authorities and freed in a prisoner exchange with the Nusra Front earlier this year.
The Associated Press contributed to this repot