A questionable racetrack deal in New York has been run through the gamut of local criminal investigators who pronounced it legal. But Sen. Alfonse M. D'Amato (R-N.Y.) and his friends who own the track have not seen the end of this case yet.

We have learned that the Senate ethics committee, which is already investigating D'Amato for allegedly helping steer federal housing grants toward his political supporters and relatives, also has the racetrack deal on its list of particulars against the senator. The ethics committee is scrutinizing D'Amato's role in helping the buyers get tax-free bonds to buy the track.

The case centers on Roosevelt Raceway, a harness track on Long Island. In 1984, four men bought the track from Gulf + Western Inc. and financed their purchase with $54 million in tax-free industrial development bonds. Such bonds are a creation of federal law and are designed to provide cheap loans to local developers for projects that will stimulate local economies.

Three of the track owners, Charles Evans, Barry Goldstein and William Hopkins, are campaign contributors to D'Amato. The fourth owner is David Stevenson. The law firm of the senator's brother, Armand D'Amato, now represents the four, although it did not represent them when they negotiated the bond deal.

Just before the purchase in 1984, Congress changed the law governing tax-free development bonds to prohibit their use for gambling enterprises. D'Amato pushed for and got a clause that allowed the bonds to be used for some gambling operations for a limited time. The Roosevelt Raceway fell into that loophole.

That's why when the FBI, the Internal Revenue Service and the Justice Department looked into the deal, they found no criminal wrongdoing. But now the ethics committee will explore the other side of the coin -- whether D'Amato broke ethics rules by furnishing the loophole.

A spokesman for the four buyers told us that they did nothing wrong, and that other tracks, not just Roosevelt, benefited from D'Amato's legislation. D'Amato refused to talk to us about the deal.

Since the four men bought the track, they have closed it and are trying to build something else on the land or sell it for substantially more than they paid for it. The terms of the bond agreement say it was supposed to remain a raceway for at least 25 years.

The industrial development bond rules also say that the bonds can be used only for projects in which the value of the raw land is no more than 25 percent of the total project value. The regulations are designed to keep people from using the bonds on speculative deals.

Our associates Amy Simmons and Scott Sleek have obtained congressional investigative documents that indicate that the land was undervalued when the buyers applied for the bonds. A congressional committee that oversees industrial development bonds is investigating whether the regulations over the money are too loose.