The attack on Thursday evening caused an outcry on social media, with many users shocked that it took place in Mumbai, widely considered to be India's safest city for women.
The woman has been admitted to hospital in south Mumbai, police said.
"Nobody has been arrested so far," a head constable at the police station dealing with the case said.
The attack took place in an abandoned textile mill in Lower Parel, a former industrial district that is now one of the city's fastest-growing neighbourhoods of luxury apartments, malls and bars. The woman was out on assignment with a male colleague.
"In the evening, the girl and her colleague were clicking pictures. Two men approached her asking her if she had permission to shoot. Another man then joined in and the photographer was gang-raped," Police Commissioner Satyapal Singh told an Indian television station. Other reports said more men were involved in the attack.
"We've brought in 10 people for questioning," Singh said.
Women's safety in India has been in the spotlight this year following the brutal gang-rape of a 23-year-old student on a moving bus in New Delhi in December, which led thousands of Indians to take to the streets in protest. The woman died of her injuries two weeks later in a Singapore hospital.
The trials of the four men and one juvenile accused of the December attack are expected to conclude within the next three weeks. The verdict on the juvenile suspect is due to be passed on Aug 31. Closing arguments in the trial of the four adult suspects started on Thursday.