The youngest person charged over the Christchurch mosque shootings video has been returned to custody after allegedly breaching his bail conditions.

The 16-year-old, who cannot be named for legal reasons, first appeared in the Youth Court in Christchurch in March.

The Herald understands police were alerted after concerns about his behaviour.

The boy's school cannot be named and his principal declined to comment, referring inquiries to police.

He was initially charged with distributing objectionable material from the mosque terror attacks and was held in custody for two months.

But he was released on bail last month with strict conditions, including not accessing the internet and not going within 500 metres of Masjid Al Noor and Linwood Mosque in Christchurch.

Last Tuesday, with the agreement of police, the teen pleaded guilty to a lesser charge of possessing the video.

He was remanded on continued bail to come back to court on July 30.

However, he appeared from custody before Youth Court Judge Jane McMeeken this morning on a new charge of breaching his bail conditions.

His lawyer Moana Cole said there had been a death in the family and the teen had been using marijuana.

Cole said a drug-screening test would be ordered and asked for a bail application to be heard on Thursday.

Judge McMeeken said she was sorry to hear about the family death but told the boy that smoking cannabis would not help, and nor would breaching his bail conditions.

He was remanded to a youth justice facility until Thursday.