While declining to discuss any specific company, Chicago Federal Reserve Bank President Charles Evans made clear that he is withholding judgment over whether a new dotcom bubble is under way. LinkedIn shares more than doubled in their first day of trading, evoking memories of the excitement surrounding Internet stocks in the 1990s and comments made by former Fed Chairman Alan Greenspan about how to recognize irrational exuberance building into an asset bubble.

We are at one of those time periods where technology is changing dramatically, people are finding ways to use the technology in amazing ways, and I have no way of knowing that those aren't just exactly the right valuations, Evans told reporters after a speech in Chicago.

Market functioning is pretty good at the moment, and so I would expect it would work out just about as well as you would expect -- which means that sometimes it's exactly the right price and other times it's higher or lower.

Analysts have faulted the Fed for keeping rates too low too long in the early 2000s, fueling the housing bubble whose collapse helped plunge the nation into its worst recession since the 1930s.

Some Fed officials, including Dallas Fed President Richard Fisher, have raised concerns that the Fed's current round of asset-buying may inadvertently fuel speculation and bubbles. Evans was asked about his views on asset bubbles after a speech in which he said the Fed should keep rates near zero for an extended period to help support the economy.

I know that some people are concerned that exuberance is coming back a little too quickly in certain market segments, he said. But regulators are keeping a sharp eye out for problems, and the Fed is also watching the situation closely, he said.

I'm hard pressed to second guess the market pricing mechanism for assets, as long as I think those markets are functioning appropriately, he said.

Federal reserve