The Ministry of Defence has apologised over an incident in which two children attending an army cadet summer camp were arrested and detained in a cell, leading to accusations of institutional racism.

An investigation has been launched into the circumstances surrounding the treatment of brothers Jabriel, 14, and Latif, 13, and the reasons why their mother was not initially informed of their arrest.

The two boys were at a week-long cadet summer camp in Northumberland when two separate criminal allegations were made against them. Jabriel was accused of racially aggravated public disorder and Latif was accused of sexual assault against a teenage girl.

Latif said the incident occurred as a group of cadets tried to take sweets from each other. He said he inadvertently touched the girl’s bottom and subsequently apologised.

Both boys said they had been subjected to racist abuse throughout the trip and that the incidents were not out of keeping with the general tenor of behaviour among the group.

The boys, from Greater Manchester, were placed into isolation before being formally arrested and handcuffed and taken to a police station an hour from the camp in Otterburn. They were then kept in separate cells until their mother arrived and they were interviewed almost 10 hours later.

After questioning, the teenagers were released. The following day the charges against them were dropped. The teenagers’ mother, Angela, originally from Jamaica, called for a full investigation, complaining of institutional racism.

“I understand they had a duty to safeguard but they also had a duty to my sons,” she said. “They are children – they also have the same rights to safeguarding and that includes informing their mother if they are being accused of something as serious as this.”

The Ministry of Defence said an investigation had been launched into the events that led up to the arrests. It said the investigation would also focus on Greater Manchester Army Cadet Force’s (GMACF) decision not to inform the boys’ mother about the allegations and arrests.

An MoD spokesperson said cadet staff contacted police after a serious allegation was made. The spokesperson apologised for the failure to contact the boys’ mother.

“We apologise for any distress this may have caused and are reviewing the manner in which the allegation was initially handled by staff. The local cadet force is now in regular touch with the family to ensure they receive a full update,” the spokesperson said.

Angela, 39, said she first became aware that her sons were no longer at the camp when she received a phone call from Northumbria police informing her they were in custody miles away.

She was only contacted by the cadets two days after her sons’ arrest when she tweeted about her experience.

She said she had been left devastated by the army’s approach and her sons were “traumatised and ashamed” after being handcuffed and arrested in front of their peers.

“They had more than one method to contact me yet they chose not to,” she said. “The first I heard was when they had already been arrested. And even after that the cadets didn’t make any attempt to contact me.”

The day after the allegations were made on Tuesday 30 July, both boys were removed from camp classes and kept in isolation with two senior cadets. They were told they were being kicked out of the institution and were asked to remove their uniforms. At about 3pm that day police arrived at the barracks and the boys were handcuffed behind their backs and taken to a station in Newcastle.

Angela received a phone call from a police sergeant informing her of the arrest. The boys were questioned and eventually released in the early hours of Thursday 1 August.

Angela said it had been a struggle initially to get her sons to attend the cadets owing to the stigma attached to the army and its perceived lack of diversity. The boys joined Stretford cadets in January.

She said she wanted them to be a positive example to other young black Caribbean children, breaking away from the “negative stereotypes that people of colour have”. She said: “Children like this often feel alienated so I wanted them to be exposed to different experiences – to show them that being part of the cadets would be a positive thing. We were realistic that there could be some issues along the way but we were sure we could overcome these. We were all so proud of them.”

Roxy Legane, the founder of Kids of Colour, who first highlighted the case, said: “During their time in the cells Jabriel willed his younger brother to go to sleep so he wouldn’t be scared. They could see excrement stains on the floor and in the courtyard. Latif read the words ‘I’ve killed five people’ on the wall. They are children.

“You cannot remove racism from decisions like these. This type of escalation in punishment towards black boys, a result of so many subconsciously viewing them as ‘threats’ instead of children, is something we see across society. GMACF must be held accountable.”

Angela is calling for the suspension of GMACF staff who dealt with her children.

Northumbria police confirmed no formal complaint of sexual assault was made and the boys were released without charge.

An army spokesperson said: “We are investigating allegations of racist remarks made by cadets and it would be inappropriate to comment further on this incident. Racism has no place in the Army Cadet Force or the wider armed forces, and we would encourage anyone who experiences it to report it.”