Five people have been arrested over suspected links to the bomb attack that wounded Yemeni President Ali Abdullah Saleh on 3 June, a diplomat in Yemen told AFP on Sunday.
Some 50 people have so far been questioned, the source said by telephone, requesting anonymity and declining to provide further details.
Saleh was flown to Saudi Arabia for treatment of wounds sustained in the attack on a mosque in his Sanaa presidential compound. He has not been seen in public since the attack, amid conflicting reports on his condition.
In an audio statement broadcast on state television on the day of the attack, Saleh appeared to blame the explosion on dissident tribal chief Sheikh Sadiq al-Ahmar, whose fighters clashed with government forces after a power transfer deal collapsed last month.
The powerful tribal chieftain denied any involvement in the attack.
Saleh's government then blamed the attack on Al-Qaeda, and others said it could even have been a drone strike because of its accuracy.
US experts on Thursday said the attack was an assassination bid, probably an "inside job" using an improvised explosive device.
STRATFOR, a US-based authority on strategic and tactical intelligence issues, said its assessment was based on an evaluation of photographs taken of the blast site.
Other top Yemeni officials, including caretaker Prime Minister Ali Mohammad Mujawar and parliament chief Abdulaziz Abdulghani, were wounded in the blast that killed 11 people and injured another 124.