CHENNAI, India — After school, when the 11-year-old girl rode her bicycle around the well-to-do apartment complex where she lived with her family in Chennai in southeastern India, an elevator attendant would find her and lead her to a basement, a rooftop or a public bathroom.

Once there, he would inject her with an orange liquid or feed her a cold drink likely laced with drugs to immobilize her, then tie a belt around her neck and rape her, she later told her older sister. He invited the complex’s security guards, plumbers and electricians to join.

Over the course of seven months, they, too, raped and molested her, possibly dozens of times, using makeup to cover any marks they left on her, her sister said.

“She was blackmailed on the edge of a pocketknife,” the 11-year-old girl’s sister, a university student, said in an interview. She said the men had told her younger sister: “If you tell your mother, we will kill her.”