The FBI has begun an investigation into the mixup of two thoroughbreds at Bowie this spring.

Larry Kolbicka of the FBI's Baltimore office confirmed yesterday that the situation is being investigated, but added, "Because it is an ongoing case, we cannot comment on it."

The case involves the switched identities of Dr. Peatoppy, a $12,000 claiming horse, and Sun Dandy, a $4,000 runner, both owned at the time by Mr. and Mrs. Joseph Palladino of Saugus, Mass. Dr. Peatoppy was later claimed by Dick Delp for Harry G. Hopkins of Darlington, Md. for $8,500.

Dr. Peatoppy ran under the name of Sun Dandy three times during the spring, a switch that was not detected by track officials even though they checked the animal's lip tattoo.

The animal's real identity was discovered by a substitute horse identifier on March 31. When the horse was brought into the paddock before the last race at Pimlico that day, Coley Blind, substituting for James Rowan, determined that the horse did not have the proper lip tattoo. The horse was scratched from the program.

Ray Stifano, who trained both horses, told Blind at the time that the horse was the same one he had raced before as Sun Dandy. It was believed the mixup had occurred when the horses had been shipped to Stifano from the Palladinos' farm, which at that time was in Essex, N.H.

As the result of an investigation this spring, Maryland racing stewards ordered purses redistributed in three races because of the switch. In addition, Rowan was relieved of his duties and reassigned.

It had appeared that the case was closed until yesterday, when racetrack personnel were summoned for questioning by the FBI. Several, including jockey Joseph Sierra, who is now living in Delaware, were subpoenaed to appear in Baltimore district court Thursday morning.

"Anybody who knows anything about racing knows that those horses were switched by accident," Sierra said.

Kolbicka declined to comment on the possibility of a subpoena, but John Pappas, head of postrace testing in Maryland, confirmed that four of his staff had been subpoenaed; he would not identify them. Rowan confirmed that he, too, had been subpoenaed.

William Ramsey, track security chief, was unavailable for comment. Neither the Palladinos nor Stifano could be reached.

The last known time the FBI investigated a horse racing matter in Maryland was 1975, when investigators looked into the celebrated Valentine's Day race fix at Bowie Race Course.

Six jockeys fixed a race that day, betting $684 to win $35,237.40. The jockeys were suspended from the track for five years following the incident.