CHICAGO, Nov. 2 (Xinhua) -- U.S. federal agents have expanded a corruption investigation first targeted at labor leaders in Fiat Chrysler to General Motors and Ford, the Detroit News revealed on Thursday.

After filing corruption charges against a former Fiat Chrysler labor executive and the wife of a late union vice president, FBI investigators have issued subpoenas in recent weeks for information about training centers financed by GM and Ford.

Several representatives of the United Automobile Workers (UAW), the biggest trade union in automobile sector in North America, are accused of participating in a 4.5-million-U.S.-dollar scheme that siphoned corporate training funds earmarked for blue-collar workers.

The training programs are operated jointly with the union, according to sources familiar with the investigation.

In an exclusive report, the Detroit News said the ongoing investigation is focused on whether training funds were misappropriated and if labor leaders at GM and Ford also received illegal benefits.

A similar scandal was first exposed when a former Fiat Chrysler labor executive and the wife of a deceased union leader were accused and formally indicted this summer for conspiring in a scheme that drained large amount of money from union training center funds.

It led to concerns in the U.S. society that big automakers might try to buy labor peace by corrupting union leaders.