The company scaled back its assessment of the problem on Tuesday, saying it had inappropriately lost track of 2 percent of the pension clients, or about 13,500 individuals, in the affected business unit. In December, MetLife said the issue could affect less than 5 percent of those clients.

Still, the update means MetLife has failed to pay pensions to two out of every 100 people in the program. Specifically, the company had given up after just two attempts to locate pensioners. The business problem, which it said began 25 years ago, is part of a unit that takes on pension obligations from employers who no longer want to manage them.

It is raising alarms among state and federal officials. The company has received inquiries from a number of state insurance and financial regulators, according to a person familiar with the matter. In response to a query, the Illinois Department of Insurance said it "is aware of the issue and is addressing it."