A group of tram drivers in Milan have been suspended from their jobs amid an investigation into a WhatsApp group in which they allegedly exchanged sexist and vulgar comments about images of female passengers.

Milan prosecutors have placed at least one employee of the city’s public transport firm, ATM, under investigation for allegedly accessing an IT system without authorisation and for hacking a CCTV system to obtain images of female passengers.

Searches of the homes of five other male employees and the confiscation of their mobile phones and other devices have been ordered, according reports in the Italian press.

The drivers allegedly commented on photos taken from CCTV that homed in on the legs, faces, breasts and thighs of female passengers.

The allegations emerged after a woman travelling on the number 15 tram on Saturday noticed an off-duty driver, still wearing his uniform and sitting in front of her, viewing a WhatsApp group chat on his phone allegedly containing such images along with sexist comments and jokes about the women’s bodies.

Realising the images had come from CCTV, which is installed on every tram in Milan for safety purposes, she took a photo of the chat on the off-duty driver’s screen and sent it to a high-profile feminist activist who in turn reported it to ATM.

ATM, which is conducting an internal inquiry, said in a statement: “ATM has acted promptly and ​with the utmost attention to fully clarify the episode, verify the proper use of company tools, protect customers and the thousands of employees who work correctly every day in service of the city.”

It is unclear whether the images came from the CCTV system on just one tram or several, or if they were shared beyond the group chat.

Marco Maria Donzelli, the president in Lombardy for Codacons, the Italian consumer watchdog which filed a formal complaint over the incident with Milan prosecutors, said: “This is a very serious incident that requires clarity, because if the facts that have emerged are confirmed, we would be faced with serious offences punishable by our criminal code, which would also pave the way for civil claims for compensation by the victims.”

The leaders of various transport unions said in a joint statement that “respect for human dignity and gender equality are essential values”.

The issue of online misogyny is prevalent in Italy. There was outrage last summer after a pornographic website featuring doctored images of prominent women, including the prime minister, Giorgia Meloni, came to light.

Meloni criticised the circulation of AI-generated deepfake images of her in May, including one depicting her in lingerie.