NEW YORK (CNNMoney.com) -- Foreign investors are still showing a voracious appetite for U.S. Treasury bonds...but they're selling everything else the United States has to offer.

According to the Treasury Department's latest report - released Thursday - overseas investors bought a total of nearly $35 billion in Treasury bonds in August.

But they dumped other securities, including corporate bonds, U.S. stocks and government-agency bonds, such as those from Fannie Mae and Freddie Mac.

The Treasury report showed that foreign investors - mostly private investors, not central banks - sold a net $29.4 billion in agency debt and $13.1 billion in corporate bonds. The outflow from equities was less pronounced with overseas investors selling only about $1 billion in stocks.

There was similar movement in July. And the latest weekly report from the Federal Reserve overseas showed investors trimming back on agency debt and increasing their holdings in Treasurys.

The selling is a possible sign of foreign investors becoming increasingly wary of any U.S. asset that isn't fully backed by the government.

And keep in mind that this latest report doesn't yet reflect the full panic that came in September.

"There have been two consecutive months of overseas investors shying away and seeking Treasurys as safe havens. I suspect this is just a preview of what we will see in September and October," said Ward McCarthy, managing director with Stone & McCarthy Research Associates in Princeton, N.J.

Another bond expert agreed that the figures for the next few months could very well show even more outflows from everything but Treasurys, despite the fact that the government essentially nationalized Fannie and Freddie last month and announced earlier this week that it is taking ownership stakes in nine of the nation's largest banks.

"It's a little bit of a concern. This is a reflection of investors panicking," said Stephen Cooke, director of credit research with SMH Capital Advisors, a Fort Worth, Tx.-based firm that primarily invests in high-yield bonds.

"There is a flight to quality and complete aversion to risk right now even though it seems the government is guaranteeing almost everything these days," Cooke added.

To be sure, it is encouraging that Treasurys are still perceived by the rest of the world as among the safest fixed-income investments out there. Despite the mess that the nation's economy is in, overseas investors haven't lost faith in the ability of the government to make due on its bonds, particularly longer-term ones.

And that's crucial considering that the United States is likely to issue more Treasurys to finance the $700 billion bank bailout plan. Still, McCarthy said it's worrisome that foreign investors don't appear to have faith in U.S. corporations.

He said that when the corporate bond market finally turns around, businesses are going to probably have to offer much higher yields than they had in the past to attract investors. That translates to higher borrowing costs at a time when many businesses are already having financial difficulties.

But there's an even bigger concern. Investors from abroad may lose interest in the corporate bond market entirely as a result of this crisis.

"If this were to persist, there could be a significant problem, especially in the corporate bond market," McCarthy said. "Overseas investors, having been burned once, may shy away from the U.S. fixed income markets in the future."

That would be terrible news. As much as many in the United States hate having to depend on foreign investments, let's face it: this is a global economy and few companies can afford to turn away much needed capital at a time like this.