Fire officials said witnesses reported seeing two male teens near the scene of the fire, which started sometime before 2 p.m. in a 1˝-story white office building used by fairgrounds and auto raceway personnel.

Six area fire departments responded to the scene, where firefighters battled the blaze for nearly three hours, bringing it under control by 4:10 p.m. and fully extinguishing it about 90 minutes later.

The deliberately set blaze consumed and incinerated the 100-foot by 30-foot frame office structure, according to Lt. Mike Mangin of the Raritan Township Fire Department, who saidfirefighters from Lambertville, Flemington, Quakertown, Amwell Valley, Three Bridges and Clinton responded to the scene.

"The firefighters were able to keep it from spreading to the raceway grandstand, its bleachers and four other buildings used for fair exhibits," said Raritan Township Fire Marshall John Smith.

"There was some minor fire exposure to some of those buildings, but they put it out. It is definitely a suspicious fire."

Fire authorities said that police spent several hours searching for the juveniles before apprehending them at an undisclosed location.

Raritan Township Police Chief Fred Brown said one of three males is a 17-year-old township resident, while one of his cohorts, also 17, is from East Amwell.

The other suspect, a 16-year-old, is from ReadingtonTownship.

The trio was picked up by police and taken into custody for questioning before being charged with the second-degree crime.

Brown said the youths, who are being detained at Warren Acres, a youth detention facility in Warren County, will be arraigned in family court this morning.

If the three are charged as adults by the Hunterdon County Prosecutor's Office, they could face 10 to 15 years in prison, police said.

Smith said the property is used as a speedway between April and October.

During the last week of August through Labor Day, it is used for the annual Flemington Fair.

There were no injuries in the blaze.