A MetLife Inc building is shown in Irvine, California, U.S., January 24, 2017. REUTERS/Mike Blake

NEW YORK (Reuters) - Metlife Inc MET.N failed to pay pensions to potentially tens of thousands of people and will have to strengthen its reserves because of the costs of finding and repaying them, the New York insurer said. Metlife said in a filing on Friday that it believed the group missing out on the payments represented less than 5 percent of about 600,000 people who receive benefits from the company via its retirement business. Those affected generally have average benefits of less than $150 a month, it said.

When taken, however, the increase to reserves could be material to Metlife’s financial results. The insurer said it would provide further disclosure on its fourth-quarter earnings call and in its annual report for 2017.

MetLife did not say how many years of missing income was owed.

The people who missed out on the payments have changed jobs, relocated or are otherwise unreachable based on currently available information, the company said, adding that it was widening its search efforts and making better use of technology.