The teenager accused of fatally stabbing three girls at a dance class in Southport has been charged with causing deadly poison and a terrorist offence, Merseyside Police’s chief constable has said.

Axel Rudakubana, 18, will appear at Westminster Magistrates’ Court via videolink on Wednesday charged with producing a biological toxin, Ricin, and possessing information likely to be of use to a person committing or preparing to commit an act of terrorism.

The charges follow searches at his home in Banks, Lancashire, Merseyside Police Chief Constable Serena Kennedy told a news conference on Tuesday.

The terror offense relates to a PDF file titled Military Studies in Jihad Against Tyrants, the Al Qaeda training manual, Ms Kennedy said.

Rudakubana is already charged with the murders of nine-year-old Alice da Silva Aguiar, six-year-old Bebe King and seven-year-old Elsie Dot Stancombe, who were stabbed to death during a Taylor Swift dance class in Hart Street, Southport, on 29 July.

He is also charged with the attempted murders of eight other children, instructor Leanne Lucas and businessman John Hayes, as well as possessing a knife.

Ms Kennedy said: “Searches at Axel Rudakubana’s home address led to the discovery of an unknown substance. Tests confirmed the substance as Ricin.

“We have worked extensively with partners to establish that there is a low to very low risk to the public and I want to clarify that assurance today.

“I can also tell you that no Ricin was present on Hart Street.”

She said it was “definitely not the case” that police had decided to keep information from the public and said she wanted to reassure communities that police were committed to getting justice and being open and transparent.

The attack has not been declared a terrorist incident by counter-terrorism police, Ms Kennedy said.

She added: “I recognize that these new allegations may lead to speculation.

“The matter for which Axel Rudakubana was charged under the Terrorism Act does not require the establishment of a motive.

“For a matter to be declared a terrorist incident, the motivation should be established.

“I would strongly advise anyone not to speculate about the motive in this case.

“Criminal proceedings against Axel Rudakubana are active and he is entitled to a fair trial.”

The police chief asked people not to get involved in “rumours and speculation”.

She said: “We must not lose sight of the families of Elsie, Bebe and Alice, who are still grieving, and the families and those victims who were present on Hart Street on July 29.

“We must do the right thing to ensure that the judicial process is not prejudiced.”

Dr Renu Bindra, senior medical adviser at the UK’s Health Safety Agency, told the press conference that experts had undertaken a thorough assessment of the risks to public health following the discovery of ricin.

She said: “There was no evidence that the victims, responders or members of the public were exposed to Ricin either as part of the incident or afterwards.

“Our initial detailed risk assessment found the risk to the community and the general public to be low.”

Rudakubana is alleged to have walked into the school holiday dance class at a small business park in Southport just before lunchtime.

Elsie and Bebe were pronounced dead at the scene. Alice was pronounced dead at Alder Hey Children’s Hospital in the early hours of the next day.

The day after the attack, thousands of people turned out for a peaceful vigil in the city, but a separate protest later erupted in violence outside a mosque in the city.

In the following week, protests took place in dozens of cities across the country and escalated into violence and riots, particularly targeting hotels in asylum centers.

Since then more than 1,000 arrests have been made and hundreds charged and imprisoned.

A tentative court date for Rudakubana has been set for January next year.