HOUSTON—Exxon Mobil Corp. said Thursday it has acquired leases in Ohio's Utica Shale, marking its first foray into a field that is thought to hold vast amounts of crude oil.

Exxon spokesman Jeff Neu said the company is "active" in the Utica Shale. He was responding to questions about a report from a publication in Wheeling, W.Va., that said scores of land owners have signed leases with the oil giant this month.

The...