In a filing, MetLife stated that those pensioners “have moved jobs, relocated, or otherwise can no longer be reached.” MetLife did not disclose in the filing how many people were involved, how long it’s been going on, how the company found out about the problem or what efforts it’s made to find the correct addresses.

All of that and more is information that the Massachusetts Securities Division is attempting to learn. “MetLife acquired the pension payment obligation from the retirees’ former employer and now bears the responsibility of making sure that retirees receive their pension checks,” Massachusetts’ top securities regulator, William Galvin, said in a statement. “Retirees cannot afford to have glitches with their pension checks. I want to uncover why this occurred and how MetLife is going to rectify the problem for the retirees.”

A Reuters report says that MetLife believes “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.”

The company also said the addressing the issue “may be material to our results of operations.”

The company is trying to pin a price tag on making good on the unpaid pensions by February 1, when it details its fourth-quarter earnings. That means tracking down all the beneficiaries and toting up the cost for all those unmade payments back to when pensioners were first eligible to receive them.

All this—the disclosure and the “ramped-up effort,” says the WSJ, “stems from a pilot project that it launched in August 2016 partly because the U.S. Department of Labor was stepping up pressure on private-sector pension plans to do a better job finding so-called missing participants,” citing company executives.