A Moscow court has detained another suspect as an accomplice in the attack by gunmen on a suburban Moscow concert hall that killed 144 people in March, the Moscow City Courts Telegram channel said Saturday.

Dzhumokhon Kurbonov, a citizen of Tajikistan, is accused of providing the attackers with means of communication and financing. The judge at Moscow’s Basmanny District Court ruled that Kurbonov would be kept in custody until May 22 pending investigation and trial.

Russian state news agency RIA Novosti said Kurbonov was reportedly detained on April 11 for 15 days on the administrative charge of petty hooliganism. Independent Russian media outlet Mediazona noted that this is a common practice used by Russian security forces to hold a person in custody while a criminal case is prepared against them.

Twelve defendants have been arrested in the case, including four who allegedly carried out the attack at the Crocus City Hall concert venue, according to RIA Novosti.

Those four appeared in the same Moscow court at the end of March on terrorism charges and showed signs of severe beatings. One appeared to be barely conscious during the hearing. The court ordered that the men, all of whom were identified in the media as citizens of Tajikistan, also be held in custody until May 22.

A faction of the Islamic State group has claimed responsibility for the massacre in which gunmen shot people who were waiting for a show by a popular rock band and then set the building on fire. But Russian officials, including President Vladimir Putin, have persistently claimed, without presenting any evidence, that Ukraine and the West had a role in the attack.

Ukraine denies involvement and its officials claim that Moscow is pushing the allegation as a pretext to intensify its fighting in Ukraine.