CINCINNATI , Ohio — Two Midwestern-based banks announced Tuesday that their companies had received shareholder approval to move forward with a proposed merger.

MainSource Financial Group, based in Greensburg, and First Financial Bancorp, based in Cincinnati, announced July 25 their plans to merge.

MainSource Bank will merge into First Financial Bank in a transaction valued at about $1 billion, the initial announcement said. The merger is expected to close in early 2018, subject to all required regulatory approvals, the companies said.

Upon completion of the merger, First Financial Bank will be the surviving entity, according to a news release Tuesday afternoon from the companies. MainSource Bank branches will continue to operate under their current name until the conversion of their operating systems, expected in the second quarter of 2018, the companies said.

Combined, the bank is anticipated to become the sixth largest bank in deposit market share in Indiana.

Upon closing, First Financial shareholders would own about 63 percent of the combined company and MainSource shareholders would own 37 percent, the original merger announcement said.

The combined company will be headquartered in Cincinnati, primarily serving customers in Ohio, Indiana and Kentucky.