For-profit higher education companies are on a spending spree for lawyers with experience in congressional investigations, as they try to respond to an expansive new inquiry into their operations.

The industry is under scrutiny after experiencing a growth spurt during the recession. More unemployed workers are trying to improve their job prospects by taking technical classes. Critics, including Sen. Tom Harkin, D-Iowa, question whether the companies have been too aggressive by exaggerating the job prospects of their graduates or by gaming the federal system for financial aid. Harkin, the chairman of the Senate Committee on Health, Education, Labor and Pensions, last month sent letters to 30 for-profit education companies asking for information about job placement rates, the cost of programs and the debt that students take on.