LAGOS, Nigeria — Nigerian officials identified six suspects arrested in connection with the June 5 attack that killed 40 people at St. Francis Catholic Church in Owo.

Maj. Gen. Jimmy Akpor, defense department spokesman, said all were linked to the Islamic State West Africa Province group. He said the arrests were made through a joint effort of military and defense officials.

Akpor said a preliminary investigation showed that “Idris Abdulmalik Omeiza was the mastermind of the terror attack on the Catholic Church in Owo as well as the attack on a police station” in Kogi state June 23. In the second attack, a police officer was killed and weapons were stolen.

Omeiza is sometimes known as Bin Malik. Police also arrested Momoh Otohu Abubakar, Aliyu Yusuf Itopa and Auwal Ishaq Onimisi for the Owo attack, in which attackers sneaked into a Pentecost Mass with explosives. Akpor confirmed Aug. 10 that the four were arrested Aug. 1.

On Aug. 11, Akpor said officials had arrested two more suspects: Al-Qasim Idris and Abdulhaleem Idris.

Officials did not release a motive for the attack.

Ondo Gov. Oluwarotimi Akeredolu said the owner of the house where the attackers stayed before the June 5 attack in Owo also had been arrested.

Nigerian Catholic officials have decried violence against Catholic targets and urged government authorities crack down on armed groups that are carrying out kidnappings and attacks on faith communities.