Ahmad al-Saqar is a person of interest to the garda investigation into the murder of Ms Carney.
The boyfriend of murdered American mother-of-one Jamey Carney has been detained in Jordan.
According to the Irish Independent, Ahmad al-Saqar is a person of interest to the garda investigation into the murder of Ms Carney.
The dramatic development came as gardai have made rapid progress in their murder probe with significant forensic, CCTV and witness evidence obtained.
Sources indicated that the 28 year old man has been detained in Jordan over the past 48 hours.
Ireland does not have an extradition treaty with Jordan and no Irish arrest warrant has been issued in respect of the Killarney murder as yet.
The detention was made by Jordan’s Public Security Directorate.
His whereabouts had been unknown.
Gardai now believe the Jordanian was with Ms Carney on Monday evening, the night she was fatally assaulted.
Ireland does not have an extradition treaty with either Jordan or Syria.
However, the US exerts enormous influence in Jordan as Washington provides over €1.3bn in military and economic aid each year to the Middle Eastern country.

Ryanair Boss Stands By His Comment Comparing Other Airlines To Rapists
The European Central Bank Announces Interest Rate Increases
Gardaí And Europol Investigate Horse Trafficking In Kildare And Other Counties
Vice Chair Of Kildare Club Believes GAA Are "Seriously Lacking Leadership"
Kildare Highlighted As Having Highest Suicide Rate In Ireland
Four HSE Regions Lose Power Over Day-To-Day Spending
Harris Prepares For First Budget As Finance Minister As FG Think-In Takes Place
Bord Gáis Energy Announce Price Rise