NEW DELHI — Oyo, a start-up that offers budget hotel rooms, has grown into one of India’s most valuable private companies and aims to be the world’s largest hotel chain by 2023.

But at least part of Oyo’s rise in India was built on practices that raise questions about the health of its business, according to financial filings, court documents and interviews with 20 current and former employees, as well as others familiar with the start-up’s operations. Many spoke on the condition of anonymity for fear of retaliation from the company.

Oyo offers rooms from unavailable hotels, such as those that have left its service, according to the company’s chief executive and nine of the current and former employees. That has the effect of inflating the number of rooms listed on Oyo’s site.

Thousands of the rooms are from unlicensed hotels and guesthouses, its executives have acknowledged. To deter trouble from the authorities over the illegal rooms, Oyo sometimes gives free lodging to the police and other officials, according to nine of the current and former employees and internal WhatsApp messages viewed by The New York Times.