Foreclosures in California soared in the second quarter to the highest level in at least 20 years, as many homeowners who bought at the height of the housing boom were unable to make mortgage payments, a real estate research firm said Tuesday.

In addition, the number of default notices — an indicator of possible future foreclosures — also jumped during the period between April and June, according to DataQuick Information Systems.

In all, some 63,061 homes were lost to foreclosure in the second quarter — the most in any quarter since 1988, when the firm began tracking foreclosures.

Foreclosures, measured by the number of trustee deeds recorded, increased about 33 percent from the previous quarter and jumped 261 percent versus the same quarter last year, when 17,458 homes were lost to foreclosure, the firm said.

The jump in foreclosures reflects the slowing housing market and the number of homes purchased with more than one loan, DataQuick said.

Notices of default, meanwhile, more than doubled in the second quarter to 121,341 loans on a total of 118,020 homes, compared to the year-ago period.

The figure indicates that some borrowers were late on payments on more than one home loan, such as a home equity line of credit.

Default notices increased 6.6 percent from the first quarter and represent the highest count since at least 1992, DataQuick said.

"The small increase in defaults from the first to the second quarter may indicate that we're nearing a plateau," John Walsh, DataQuick's president, said in a statement.

Mortgage defaults have been on the rise statewide since fall 2005, coinciding with the start of a slowdown in sales and a decline in home prices.

Sales of foreclosed homes have been rising this year, but home prices have continued to slide, making it harder for homeowners who fall behind on payments to sell their homes and clear their debt.

Most of the home loans that slipped into default in the most recent quarter were made between September 2005 and November 2006, as the housing boom wound down.

During that period, which saw speculation-fueled sales in inland areas, many borrowers financed homes with more than one loan.

The median age of home loans in default increased to 26 months in the most recent period, compared to 16 months in the same quarter last year.

The median amount of the primary home loans in default was $346,400. The median amount homeowners fell behind was $11,583, the firm said.

Borrowers who took out home equity loans owed a median of $3,492 on a median credit line of $60,000.