Three prized show dogs were found dead along a Prince George's County road yesterday morning, killed when the cages they were in were apparently hurled from a speeding stolen van. Seven other dogs thrown from the vehicle survived and two others were still missing early today.

A spokesman for one dog owner put their value at $15,000 to $20,000 apiece.But other specialists said the dogs were probably worth somewhere between $500 and $8,000 each, depending on breed and show history.

The 12 dogs, of various breeds and sizes ranging from a Dalmatian to a miniature Doberman, were stolen while on their way to compete with about 1,700 other at an exhibition staged yesterday by the National Capital Kennel Club at Rosecroft Raceway.

Sid Lamont, a professional handler from New Jersey, had parked the van outside the Sheraton Northeast Hotel in New Carrollton early yesterday morning to register. When he stepped out of the building about 3:30 a.m., he found the van and dogs missing.

Later in the morning, police acting on a tip found the three dead dogs alongside Governor Bridge Road in Mitchellville, and rounded up seven others running free nearby. Smashed cages found at the scene indicated that they had been shoved off the back of the truck while it was moving.

The dogs found dead were all miniature, hand-held breeds. The surviving animals were taken to a veterinarian for examination.

Two dogs -- a Dalmatian answering to the name Lilah and a cream-colored, shaggy Tibetan terrier named Josh -- had not been located as of early this morning. A reward is being offered for information leading to their recovery. The van is still missing.

A spokesman for the owner of one of the dogs said all were top-flight champions and had just come from a show at Madison Square Garden in New York.

Shows like the one there and at Rosecroft yesterday judge dogs according to how well they meet standards of physical perfection for their breed. Dogs can also be ranked on obedience. By consistently placing high in such shows, dogs become increasingly valuable on the market.

Persons with any information about the incident or the dogs are asked to call county police at 699-2610.