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NEW YORK, April 30 (Reuters) - The balance of troubled U.S. commercial real estate loans soared by 48 percent last quarter to $23.7 billion, with the largest on the list dominated by multifamily properties hit by the weakening economy, Fitch Ratings said on Thursday.

The number of loans sent into "special servicing" will jump again this quarter, with more than 150 properties included in the bankruptcy of No. 2 U.S. mall owner General Growth Properties Inc (GGWPQ.PK: Quote, Profile, Research), Fitch said in a report.

A $130.5 million loan backed by 11 multifamily properties in Georgia, North Carolina and Virginia was among the largest delinquent mortgages to be pushed into special servicing last quarter, as high unemployment and economic conditions left many tenants of the 2,904 units short on rent, Fitch said.

The loan is in Merrill Lynch's MLMT 2007-C1 commercial mortgage-backed security, issued at the peak of the real estate boom when underwriters had loosened standards to feed growth in CMBS. Investors have been dumping CMBS since late 2008 amid expectations that the recession would reduce revenue from the properties and expose weakness in underwritings.

CMBS have rallied over the past several weeks amid expectations that a federal lending program will provide cash for investors willing to buy the bonds, helping reduce interest rate to levels that encourage fresh lending.

Prices had also dropped to levels that compensate for the risk that commercial property revenue and value would decline more, analysts said.

A special servicer specializes in managing commercial properties in or near distress. In total, 497 loans were transferred to the servicers last quarter, Fitch said.

"This dramatic increase in just three months illustrates the rapidly declining performance of commercial mortgage-backed securities transactions," the ratings agency said.