In the latest indication of how daunting it has been to remake the troubled New York City jails, the de Blasio administration is spending an additional $7 million on an international consulting firm that it first hired in 2014 to develop a blueprint for reform.

While the consultant, McKinsey & Company, specializes in reorganizing corporations, it has rarely if ever worked in jails or prisons before the Rikers Island jail complex. The firm’s consultants — often youthful graduates of elite universities — are expected to focus on measures to reduce the violence, which persists even as the city spends tens of millions of dollars to improve conditions.

Officials declined to describe how many consultants would be involved or what services would be provided by McKinsey, which was first hired by the city in September 2014 for $1.7 million.

The department “is committed to creating a culture of safety within the city’s jails, and extending our current contract with McKinsey is part of that ongoing effort,” a Correction Department spokesman said in a statement.