WASHINGTON – A little-known reward for brokers who arrange home loans at high interest rates is drawing scrutiny from law-enforcement authorities, who say these bonuses can cost unwitting homeowners thousands of dollars over time.

Lenders pay the bonuses to independent brokers who sign up borrowers for mortgages at higher interest rates than they qualify for. With these brokers writing an estimated 60% of home loans in America, regulators are concerned that many people are being steered into higher-rate loans without being aware of the higher costs.

“With the growing role of mortgage brokers, my office and attorneys general around the country have focused increased attention on these lending arrangements,” the California attorney general, Bill Lockyer, said in a statement to the Los Angeles Times. “We will be monitoring the market to ensure abuses do not occur.”

The bonus – typically worth thousands of dollars – is included in most loans written by independent brokers, some industry experts say, and may be especially prevalent in costlier mortgages that brokers arrange for borrowers with weak credit.

In some cases, customers knowingly accept the higher rates. Homeowners who plan to sell or refinance in a year or two, for example, can often save money by taking a higher-interest loan and lowering their upfront closing costs.

But homeowners who settle on a higher rate and plan on staying put can spend thousands of additional dollars over time. Consumer advocates and regulators say this trade-off is often not understood by borrowers.They also caution that brokers may not always make clear that they are rewarded by the lender for loans with higher interest rates.

Mr. Lockyer is part of a nationwide task force of prosecutors that in January announced a $325 million settlement by Orange, Calif.-based Ameriquest Mortgage Company for al leged deceptive lending practices. Under that agreement, Ameriquest’s loan agents cannot profit from bumping customers into loans at higher rates.

A leader of the task force said that the practices of independent brokers are an emerging focus,although no cases are imminent. Up to now, investigators have concentrated on retail lenders, such as Ameriquest, who deal with customers directly.

“We want to look at it, because it may constitute a deceptive practice,” said IowaAttorney General Tom Miller, who led the Ameriquest case. “Consumers are paying more than the fair market price of their loan.”