A school principal and an attendant have been arrested in India after allegations that female students were stripped naked to check if they were menstruating after blood stains were found on a toilet wall.

The police action came after the mother of one of the "10 to 15 girls" who were put through the alleged humiliation lodged a complaint.

The incident took place on Tuesday in a village not far from Mumbai city. On Wednesday, parents protested at the school, demanding strict punishment against the authorities.

In a video, the school principal is seen arguing with angry parents - she denies that she ordered a strip-search or that it took place.

Senior police official Milind Shinde told the BBC on Thursday that they were investigating the allegations. The arrested women would be produced in court later in the day, he said.

The police complaint names four other teachers and two trustees of the all-girls school in Thane in the western state of Maharashtra. BBC has reached out to the school authorities for a response.

In their complaint, police have invoked sections of the law that deal with assault and intent to outrage modesty of women. They have also added sections from the stringent Pocso (Protection of Children from Sexual Offences) Act.

The parents have alleged that all the students from 5th to 10th classes - who would be between the ages of 10 and 16 - were summoned to a hall by the school principal on Tuesday.

There, they were shown photos from the toilet on a projector, including that of a hand stain, and those who had their periods were asked to raise their hands. A teacher collected hand prints of all those who did.

At least 10 to 15 girls who said they weren't menstruating were then taken to the toilet, forced to strip and went through an inspection.

The child whose mother lodged the police complaint has alleged that her daughter, who didn't have her period, was scolded and asked why she wasn't wearing a sanitary pad. Her hand print was also collected.

She said her daughter "felt very ashamed" because of what had happened.

Some of the parents told the BBC that their daughters were traumatised.

"The incident raises serious questions about the safety of our children. Our girls are very afraid. The government should take strict action against the school," one parent said.

The mother of one of the students told BBC Marathi that when confronted, the principal denied everything. "But the school didn't have an answer when we asked them whether so many girls could be lying," she said.

Periods have long been a taboo in India where menstruating girls and women are considered impure and excluded from social and religious events.

And incidents of shaming female students have been reported in the past too.

In 2017, 70 students were stripped naked at a residential school in Uttar Pradesh by the female warden after she found blood on a bathroom door.

In 2020, 68 students living in a college hostel in Gujarat were strip-searched after they stopped reporting their periods to authorities to avoid restrictions which barred them from entering the temple and the kitchen or touching other students.

At meal times, they had to sit away from others, and in the classroom, they were expected to sit on the last bench.

The regressive ideas are being increasingly challenged by urban educated women, but success has been patchy and women in many parts of the country continue to face discrimination.