Topping last week's haul of nearly $10 billion, tax-free money market funds raked in $11.9 billion, setting a record high of $511.5 billion in total assets for the week ending May 12, according to the Money Fund Report, a service of iMoneynet.com of Westborough, Mass.

This week's total assets trumped the previous high of $504.8 billion set on April 7, according to the report. Last week, the funds took in $9.98 billion to settle at $499.5 billion in assets.

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