Four persons have been arrested in a Fairfax County jewel robbery after an investigation that centered on the robbers use of an empty pizza box.

Authorities said information obtained during the investigation also indicated the possible existence of a loosely knit group that might be linked to as many as 100 Northern Virginia crimes.

In the robbery, antique South American jewelry was taken April 13 from Helga Schweikert of Springfield after she was seized from behind while talking to a visitor at her house, according to county police spokesman Warren Carmichael.

Carmichael said someone earlier had said he would bring a pizza to Schweikert's house for them to share while discussing a job he was offering. When the visitor arrived, Carmichael said, he brought a pizza box, but the box was empty.

In a key step in the investigation, Carmichael said, police located an employe in an Annandale pizza parlor who recalled selling an empty pizza box for 25 cents.

Subsequently, he said, police arranged an undercover operation in which they were able to buy the jewelry allegedly taken from Schweikert. She valued the jewelry at $150,000, the spokesman said.

Carmichael said four persons were ultiamtely arrested and charged with robbery in the theft of the jewelry from Schweikert.

They were identified as Christine Owens, 53, of 10604 Reid La., Nokesville, Va., who was described as a horse breeder; Carl L. Gentry, 36, of 113 Denver Dr., Manassas Park, Va.; Bent Pedersen, 41, 6017 Lebanon Dr., Falls Church, and Donald R. George, 34, of 7906 Maplewood Dr., Manassas, Va.

Carmichael said information from the investigation that led to their arrests had also led police to suspect the possible existence of a "loosely connected group" of more than a dozen persons that may have been involved in crimes dating back to 1969 in Fairfax, Orange, Loudoun, Fauquier and Prince William counties.