Utica, NY (WIBX) - Utica fire marshals are working around the clock to determine what sparked Monday's deadly fire on Schuyler Street, fire chief Russ Brooks said Wednesday.

"They've sent articles out to labs to be analyzed and following up on leads. At this point, I'm optimistic that they will determine an exact cause and origin," he said.

The fire killed Leida Santiago, 32, and three of her young children ages 1, 2 and 4.

Oneida County Coroner Stephen Wolanin told the Utica Observer Dispatch that all four died of smoke inhalation.