Suspects in the Nigeria church attack have been detained by a regional security force, the authorities there say.
Gunmen stormed the St Francis Catholic Church in Owo, Ondo state, during a service earlier this month and opened fire.
The suspects are being held by a force set up by the south-west state governors, known as Amotekun. It is a separate organisation from the police.
Amotekun commander Adetunji Adeleye told the BBC that the suspects were at different stages of interrogation.
He did not give any details about those being held but said a vehicle and some weapons were recovered.
Amotekun will need to hand the suspects over to the police if they are going to be prosecuted as it does not have the power to take people to court.
As well as the at least 40 people who died on 5 June, more than 100 others were injured during the attack.
The Nigerian government blamed the killings on the militant group, Islamic State of West African Province (ISWAP). But the jihadists have not said that they carried out the attack.