No further police action will be taken against three men arrested after an investigation into an Islamic school for girls in Lancashire.

Two men arrested on suspicion of sexual assault and false imprisonment have been released from their bail without charge, police said tonight.

A third man arrested on suspicion of false imprisonment at the school in Lancaster has also been released without charge.

Police were called to the Jamea Al Kauthar school to investigate claims of sexual assault and false imprisonment.

Detectives executed a search warrant and arrested the three men earlier this month.

Today police said no further action will be taken as "none of the conduct disclosed ... meets the threshold for criminal prosecution".

The investigation concentrated on one incident that allegedly took place a fortnight ago, and this led to significant questions about safeguarding processes at the school, the police said.

A Lancashire Constabulary spokesman said: "Clearly we have a duty to respond to information received and that is what we have done in this case, as sensitively and proportionately as possible, so that we could ascertain the circumstances surrounding the information we received.

"Our priority is the protection of vulnerable people and given the same information again we would act in the same way.

"We also have a safeguarding responsibility outside of that investigation, along with partners and regulators, and are duty bound to make sure that the right processes are in place at the school to protect the welfare of pupils. With that in mind we have asked Ofsted and other partners to look into some of these processes."

John Dilworth, head of the complex casework unit with CPS North West, said: "I have reviewed a file of evidence submitted to me by Lancashire police in relation to an investigation into a recent alleged incident at the Jamea Al Kauthar School in Lancaster. After carefully reviewing all the evidence I have advised the police that there is insufficient evidence to provide a realistic prospect of conviction on any criminal charges.

"During the course of their investigation, police conducted interviews with the relevant students, who were all over 16, and no complaints were made. The original witness complaint that was made does not provide a realistic prospect of conviction and no further evidence became available.

"I am aware that Lancashire Constabulary is in contact with the relevant agencies to address any potential safeguarding issues arising from this investigation."

According to its website, the independent boarding school aims to educate Muslim girls over the age of 11 "in a safe, secure, happy and Islamic environment".