The company of Scott Boras, baseball’s pre-eminent agent, provided tens of thousands of dollars in loans and payments to the families of poor Dominican teenage prospects, according to people with ties to Mr. Boras, raising questions about whether the company exploited the prospects and violated the rules of the Major League Baseball Players Association. The union, which oversees agents and restricts many such transactions because they create a financial tether that can lead to the player’s becoming indentured, can levy penalties ranging from a fine to revoking an agent’s right to represent players, sports law experts said.

“The money obligates them to the agent, gives the agent leverage, and coerces the athlete to do what the agent wants because of fear of foreclosure or other adverse consequences for the athlete or the athlete’s family,” said Mark S. Levinstein, a prominent sports lawyer who is a partner at the Washington law firm Williams & Connolly.

According to the union’s regulations governing agents, loans of more than $500 a year to players and their families are prohibited unless the purpose of the loan is disclosed to the union.

A spokesman for the players union declined to comment on whether the loans made by Mr. Boras’s company had been registered with the union. In a statement, Mr. Boras declined to say whether any loans were made, although he did say his company had “aided” players and families in the past.

In a written statement, a spokesman for Major League Baseball said, “This is a serious issue that raises concerns about the business practices of agents who have played a prominent role in the game.”

Domingo Ramos, a former major league player who works for Mr. Boras’s company in the Dominican Republic, said in an interview that the company normally represented a handful of top prospects each year and made loans to a majority of them. The money was typically used for housing, food and other necessities, he said.

“Like I say, sometimes we get it back, sometimes we don’t,” Mr. Ramos said. “Sometimes it’s tough to get it back. It’s as simple as that.”He added, “But we thinking about helping the kid out and retain him as a client.”

In the case of Edward Salcedo, a can’t-miss shortstop prospect who agreed around age 15 in 2006 to be represented by Mr. Boras, the loans gave the Boras Corporation significant leverage. From 2007 to 2009, the company provided payments to Mr. Salcedo and his family, according to Mr. Salcedo; his brother, Thommy; and a former Boras employee, Martiris Hanley. The loans eventually totaled about $70,000, which went for rent, food, other necessities and Thommy Salcedo’s college education, Thommy Salcedo and Mr. Hanley said. The money was to be repaid from Edward Salcedo’s future earnings, Thommy Salcedo and Mr. Hanley said.

But the Salcedos hired a new Dominican trainer in 2009 because they believed Boras could not help them resolve questions that had arisen about Edward Salcedo’s age. That trainer, Edgar Mercedes, prepared him for tryouts with major league teams, and Mr. Salcedo received a $1.6 million contract from the Atlanta Braves last February.

Days later, an employee of Mr. Boras’s called the family demanding immediate repayment of the loan, Thommy Salcedo said. He added, “We thought that if we went with another agent, Boras was going to put more pressure on us for this money, and my mother had so much debt that she couldn’t pay it.”Edward returned to Mr. Boras, Thommy Salcedo, 21, said.

“We loan Salcedos,” Mr. Ramos said. “We haven’t get that back, but we’ll get it back.”Edward Salcedo, 19, who struggled in 54 games this season for Class A Rome in Georgia, said he was still represented by Mr. Boras and had not repaid the money.

In the statement, Mr. Boras said that the company had aided the Salcedo family “in their time of need,” and said it was “something that we’ve done for other clients in the past, always consistent with” the rules of the union.

Mr. Boras said the aid to the family came as a legal remedy was pursued to the questions raised over Edward Salcedo’s age. That statement, however, appeared to contradict the accounts of Thommy Salcedo and Mr. Martiris, who said the loans began before age questions arose.