PITTSBURGH — A man who owns property at the site where Flight 93 crashed has demanded millions for his portion of land where a memorial is planned, and has installed a donation box to help pay for security.

The actions by Mike Svonavec have angered victims’ families, who believe he is overcharging and disagree with the need for a donation box.

“That land has been paid for with 40 lives … the donation box is an insult to that cost,” said Patrick White, vice president for Families of Flight 93.

Mr. Svonavec wants $10 million for his 273-acre property in Somerset County, far more than the per-acre amount paid for nearby land, Mr. White said Tuesday. He said Mr. Svonavec told him about his asking price last July, and that he has rejected three offers from the group — the latest for more than $500,000.

“I think Svonavec believes his land, because it has the blood of my cousin and 39 other people, it’s worth more,” said Mr. White, referring to his cousin, Louis “Joey” Nacke II, a passenger.

Mr. Svonavec, who operates a stone quarry, said he wants fair market value for the parcel but would accept no money for the exact site where 40 passengers and crewmembers died when the hijacked United Airlines flight crashed on September 11, 2001. He declined to comment on the $10 million figure.

The donation box, installed near a temporary memorial on the land, would help cover security costs. Security has been handled by a firm at a cost of about $10,000 a month since federal funding ran out in February. The site has also incurred other costs, he said.

“I just can’t afford it,” Mr. Svonavec said. “I need some help.”

Memorial planners have purchased 60 of the 1,300 acres needed for a permanent memorial and national park. Mr. Svonavec owns the second-largest parcel of land in the area after PBS Coals Inc., which owns 864 acres.

Mr. White said he is negotiating with PBS Coals, and the remaining parcels are in various stages of being acquired.

Mr. Svonavec said he is working with advisers, including Randall Bell, a California-based real estate appraiser who specializes in properties where disasters have occurred. Mr. Svonavec said he is waiting for a completed appraisal.

Mr. Bell has handled properties including the mansion where 39 Heaven’s Gate cult members committed suicide in 1997 and the house where 6-year-old JonBenet Ramsey was found strangled the previous year.

Mr. Svonavec said he had asked to deal exclusively with the National Park Service, which also is working on the memorial, because he feels “very uncomfortable” negotiating with the family group.

“I did not want it to become an emotional issue,” Mr. Svonavec said. “I do know we have been cooperative with all parties.”

He said he rejected an earlier Park Service offer because “it just wasn’t acceptable.” It was based on an internal, not an independent, property appraisal, he said.

The Park Service is preparing another appraisal. Joanne Hanley, the Park Service superintendent of the site, declined to comment.

Mr. Svonavec said he would consider leasing the land or selling it to another entity, but that he believes a memorial is fitting. Meanwhile, he said he intends to keep the donation box in place.

Donna Glessner, one of 43 volunteers who guide visitors at the site, said visitors were being advised about the donation box, but that some people had placed money in the box without realizing the funds would go to Mr. Svonavec.

“They’re alarmed that they may have given their money to something that they didn’t want to give their money to,” she said.

Flight 93 was en route to San Francisco from Newark, N.J., when it was hijacked and crashed in a field near Shanksville as passengers rushed the cockpit, according to the September 11 Commission.

The memorial was established as a national park through an act of Congress in 2002. A temporary memorial that includes a 10-foot-tall chain-link fence has been erected near the crash site, which is not open to the public.

Construction of a $58 million permanent memorial is scheduled to begin by early 2009, and a ribbon-cutting ceremony has been planned for the 10-year anniversary of the attacks.