Kenneth R. Lench, the chief of the structured and new products unit at the SEC’s division of enforcement, is leaving at the end of the month.

A 23-year veteran of the Enforcement Division, Lench headed the unit since it was established in 2010, in the aftermath of the financial crisis. The unit, which is composed of 45 staff members, is charged with investigating complex financial instruments like asset-backed and derivative securities.

In Lench’s three years at the helm, his office issued a number of enforcement actions against financial services firms related to collateralized debt obligations and residential mortgage-backed securities, filing cases against Goldman Sachs, Citigroup, JPMorgan Chase and Credit Suisse, among others. Through these measures, the unit recovered about $1.7 billion for affected investors, according to the SEC's announcement on Tuesday.

“Ken’s determination to always seek the right answers and his devotion to protecting investors by working tirelessly with his staff and colleagues made everyone around him better,” George S. Canellos, co-director of the SEC’s Division of Enforcement, said in a statement. “The enforcement division is stronger today because of Ken’s unwavering leadership.”

Lench joined the SEC's enforcement division as a staff attorney in 1990. Named assistant director in 2004, he led a number of investigations into accounting, financial and hedge fund fraud, as well as violations of the Foreign Corrupt Practices Act, securing settlements with Ernst & Young and Bally Total Fitness, among others.

Deputy chief Reid A. Muoio will head the structured and new products unit on an interim basis until Lench’s permanent successor is named.

“It has been a privilege to lead such a talented and dedicated team of professionals committed to uncovering wrongdoing in our securities markets,” said Lench, who is leaving to join the private sector. “I am fortunate to have had the opportunity to work on significant and challenging cases on behalf of our nation’s investors.”