More than 20 firearms, including machine guns and long-range rifles, belonging to a Marshall gun dealer were stolen Sunday night from a truck in a Philadelphia suburb, federal authorities said.

The truck was parked at a restaurant in King of Prussia when the firearms were taken. The dealer had just left a gun show at the Valley Forge Convention Center and had stopped for dinner before heading back to Western Pennsylvania.

The firearms belonged to Arms & Ordnance of Commonwealth Drive in the Warrendale area of Marshall, according to John Hageman, a spokesman for the Philadelphia division of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

F. Charles Logan, the store's owner, didn't return several calls seeking comment yesterday.

Upper Merion Township police, who responded to the burglary on Sunday, said in a news release that the firearms were valued at more than $200,000.

Mr. Hageman said he could not confirm that figure. ATF agents planned to meet with Mr. Logan at his store today to get a complete accounting of each stolen firearm. Agents also were working with local police to follow up on any leads in the case.

The agency is offering a $10,000 reward to anyone who has information.

The stolen firearms include at least several fully automatic machine guns, Mr. Hageman said, although he was unsure of the models.

Mr. Logan has a Class III federal license that enables him to sell machine guns, meaning he pays $500 a year on top of regular dealer license fees.

"I buy, sell, trade, and broker NFA [National Firearms Act] and other exotic firearms. I can offer long lists of references and satisfied customers at your request," says the dealer's Web site, www.arms-ordnance.net.

There was another burglary of a gun dealer at the Valley Forge Gun Show in September, Mr. Hageman said.

Anyone with information about the latest burglary is asked to call ATF at 1-800-283-4867 or Upper Merion police at 610-265-3232.