More than two weeks after Hurricane Katrina, the American Red Cross said yesterday it has collected $610 million in donations and channeled about one-third to the stricken region, though it cannot yet say exactly how the money was spent.

The Red Cross donations account for 80 percent of the $788 million in hurricane relief contributions, a pace of giving greater than any in U.S. history, according to the Chronicle of Philanthropy, which tracks post-disaster relief totals. In recent days, though, the volume of contributions has begun to slacken. That could present a problem for the Red Cross, which so far has raised about half of what the organization estimates it will need for hurricane relief, as well as for other charities.

"We're already seeing that people's interests are shifting, which is sad," said Katya Andresen, vice president of marketing for Network for Good, a leading online giving site. Daily hurricane relief donations made through the site have dropped 30-fold from a peak of nearly $3 million Sept. 1. "People see the images on television and feel a great sense of emergency," Andresen said. "But while the sense of immediacy passes, the need doesn't."

As of yesterday, the Red Cross had spent $140 million on assistance, including food, shelter, transportation of staff to affected areas, mental health counseling and financial assistance to survivors, said Red Cross development spokeswoman Kara Bunte. She said an additional $70 million is en route to 50 chapters in the affected region.

The Red Cross "does have procedures in place to account for [spending on] this and other disasters, but over the last two weeks we've given guidance to our chapters to focus on service delivery" rather than "counting beans," she said.

"I think the organization has shown great strength . . . but it is challenging," Bunte added. "We are being as flexible as we can in terms of providing aid."

Strained from the start by the biggest single response effort in its 124-year history, the Red Cross said it has housed more than 207,000 survivors of the storm in 709 shelters across 24 states and the District, according to the charity's Web site. It has worked with the Southern Baptist Convention to serve 7.6 million hot meals and has trained 63,000 volunteers to help 74,000 relief workers in the stricken area. But spending on those individual efforts is something "we're still trying to get a handle on," Bunte said.

The scant detail, charity watchdogs said, is as much because of a lack of governmental reporting requirements as it is a reflection of the scope of the disaster.

"The market dictates what charities report and what they don't . . . but the government demands nothing" beyond an annual informational return, said Trent Stamp, executive director of Charity Navigator, which monitors charitable groups.

Daniel Borochoff, president of the American Institute of Philanthropy, said the Red Cross "could do a better job of giving some sort of breakout."

"But you don't want to be too hard on them because of what they have to deal with," Borochoff said.

The Red Cross estimates it will need $1 billion to $1.6 billion to meet hurricane survivors' needs for immediate relief.

The pace of contributions, sped by online giving, has far outstripped the response to the Sept. 11, 2001, attacks and the Asian tsunami over the same length of time, but the total still falls far short of giving after those events. In the aftermath of the 2001 attacks, Americans gave charities $2.2 billion, according to the Chronicle of Philanthropy. After the tsunami, they donated $1.3 billion.

After the Sept. 11 attacks, "two weeks out, the total was about $500 million, and the grand total was five times as much" by early 2002, said Patrick Rooney, director of research at Indiana University's Center on Philanthropy. "So if you're projecting on past practice, giving to hurricane relief should continue for several months."

The question, Rooney said, is whether "donors and funders will be able to sustain that rate of giving once they move past the immediate disaster relief, to rebuild cultures and communities and families."