Sources also told ESPN that the investigation is expected to implicate roughly 20 people on "a handful" of teams before it is complete. Investigators also have expanded their probe into Venezuela, where many major league clubs have player academies. "Things are coming to a head," one source familiar with MLB's investigation said.

Four MLB investigators returned to the United States from the Dominican last week and are preparing a report for the commissioner's office. One source briefed on MLB investigators' findings said he believed "less than a half-dozen" teams would be implicated, including the Yankees, Red Sox, Nationals and White Sox.

The scandal began to break in March when Wilder, then the scouting director for the White Sox, was stopped in Miami by U.S. Customs officials while trying to bring about $40,000 in cash back from the Dominican Republic. Sources said Wilder, who has not been criminally charged, has been cooperating with the FBI. He and two scouts were fired by the White Sox in May.

Wilder and others have been accused of inflating the value of some Dominican prospects, then demanding a kickback from the players' families once the players were signed.