Three men have been arrested over claims of sexual assault and false imprisonment at an Islamic school for girls.
Specialist female police officers are conducting searches at the Jamea Al Kauthar school in Lancaster after a report was received over concerns for the welfare of a "small group" of teenage pupils.
A 40-year-old man from Bolton and a 30-year-old man from Blackburn have been arrested on suspicion of sexual assault and false imprisonment, Lancashire Police said.
A 53-year-old man from Blackburn has been held on suspicion of false imprisonment.
All three men are being questioned in custody.
A spokeswoman for Lancashire Police said: "We are still at the very early stages of the investigation and our aim at the moment is to respond to the concerns raised proportionately, in a measured way and with sensitivity.
"Searches at the school are being conducted by specialist female officers with sensitivity and are being carried out as quickly as possible to ensure minimum impact.
"We are working closely with the school and the local authorities to establish the circumstances around exactly what has taken place and we have specialist officers supporting the victims."
Police would not confirm whether the men arrested were members of teaching staff at the Ashton Road site.
In a statement on its website, Jamea al Kauthar said: "The school is aware of the allegations that have been made and at the present moment the school is fully co-operating with the police with their investigations into the matter.
"The school will publish a statement of any details it receives, once this has been received. We expect the matter to be cleared up soon."