The number of U.S. homes heading toward foreclosure more than doubled in the first quarter from a year earlier, as weakening property values and tighter lending left many homeowners powerless to prevent homes from being auctioned to the highest bidder, a research firm said Monday.

The hardest hit states were Nevada, Florida, and California. California's Stockton led the nation with a foreclosure rate that was 6.6 times the national average RealtyTrac Inc. said.

Nationwide, 649,917 homes received at least one foreclosure-related filing in the first three months of the year, up 112% from 306,722 during the same period last year, RealtyTrac said.

The latest tally also represents an increase of 23% from the fourth quarter of last year.

That means that one in every 194 households received a foreclosure filing during the quarter. Foreclosure filings increased in all but four states.

This is the seventh consecutive quarter of rising foreclosure activity, RealtyTrac noted.

"What would normally alleviate the foreclosure situation in a normal market is people starting to buy properties again," said Rick Sharga, RealtyTrac's vice president of marketing.

However, the unavailability of loans for people without perfect credit and a significant down payment is slowing the process, he said.

"It's a cycle that's going to be difficult to break, and we're certainly not at the breaking point just yet," Sharga added.

Nevada posted the worst foreclosure rate in the nation, with one in every 54 households receiving a foreclosure-related notice, nearly four times the national rate.

California had the most properties facing foreclosure at 169,831, an increase of 213% from a year earlier. It also posted the second-highest foreclosure rate in the country, with one in every 78 households receiving a foreclosure-related notice.