Alipore: Police on Wednesday submitted in court a chargesheet mentioning "gang rape" against the two physical training teachers accused of sexually assaulting a four-year-old student of a girls' school in Regent Park last year.

Co-accused Abhishek Roy and Mohammad Mafisuddin have been charged under Section 376D (gang rape) of the Indian Penal Code and sections 4 and 6 of the Protection of Children from Sexual Offences (Pocso) Act, 2012. The last two sections deal with "aggravated penetrative sexual assault".

If convicted, the physical training teachers are liable for a maximum punishment of imprisonment for life.

The 287-page chargesheet was submitted before Sanjeev Daruka, the seventh additional sessions judge of Alipore, on the 90th day since the first arrest was made in the case. The document mentions 27 witnesses in the case, mostly to substantiate the sequence of events that led to the alleged incident.

Roy and Mafisuddin were arrested after the victim identified them from photographs shown to her on a mobile phone. They have been in judicial custody since their arrest on December 1.

According to the girl's statement before the police, both physical education teachers sexually assaulted her in a washroom on the school campus on November 30.

The police have started a separate case against the former principal of the school, charging her with cheating, causing disappearance of evidence, criminal conspiracy, failure to report an offence by subordinates and disclosing the name of the victim in public. The probe in this case "is in progress", a senior police officer said on Wednesday.

After an agitation by guardians, a committee comprising officials of the state education department, the commission for child rights protection, the ICSE board and the police was formed in December to probe the allegations.

Schools in Calcutta have been rocked by a series of allegations about sexual assault on children, at least two of them involving teachers.