The Metropolitan Museum of Art, facing increasing scrutiny from law enforcement officials, academics and the news media over the extent to which its collection includes looted artifacts, announced on Tuesday a major new effort to review its holdings and policies with a view toward returning items it finds to have problematic histories.

The core feature of the new plan is the museum’s decision to hire a provenance research team that is as robust as any in place at an American museum.

The moves come as the Met — one of the largest museums in the world, with more than 1.5 million works from the past 5,000 years in its holdings — has been buffeted in recent years by increasing calls to repatriate works that law enforcement officials and foreign governments say it has no right to.

In the past year, Cambodian officials have sought the help of federal officials to secure the return of artifacts they view as looted. Separately, the Manhattan district attorney’s office has seized dozens of antiquities from the museum to return them to countries like Turkey, Egypt and Italy.