A cigarette lighter may have caused a fatal fire at a nursing home in the Upper Peninsula of Michigan in December.

While a lighter is believed to be the culprit, that information has not been confirmed, according to the Michigan Department of Community Health. Two residents of the Mather Nursing Center died in the blaze.

The facility, which was cited for 13 violations by fire investigators and for many more by the Department of Community Health, could reopen this week. The department is requiring that the facility fix only its most urgent problems before reopening.