Dec. 11 (Bloomberg) -- Florida's top finance official asked for an investigation of policies that led the state's local government investment pool to invest in securities tied to the subprime mortgage market.

State Chief Financial Officer Alex Sink, in a letter yesterday to Florida's inspector general, Melinda Miguel, asked for a probe of whether the State Board of Administration's securities purchases violated its investment guidelines. Cities and schools withdrew $13 billion from the $27 billion fund last month after learning it held subprime-tainted debt that had defaulted or been downgraded.

``It is essential that the state does all it can in an attempt to restore confidence'' in the management of the pool, Sink said in her letter.

The board hired BlackRock Inc., a New York-based money management firm, to restructure the fund and manage it on an interim basis. Under BlackRock's plan, $2 billion of the weakest securities were walled off from the rest.

Sink also asked Miguel to look into who sold the assets to the pool, when the securities' ratings were cut and the board's disclosure requirements for downgraded investments. The state board's audit committee, of which the inspector general is a member, is scheduled to meet tomorrow.

Sink is a trustee of the state board along with Governor Charlie Crist and Florida Attorney General Bill McCollum. The board is scheduled to meet at 3:30 p.m. today in Tallahassee. An advisory committee of investors was also to meet at midday.

To contact the reporters on this story: Darrell Preston in Dallas at dpreston@bloomberg.net.

Last Updated: December 11, 2007 12:35 EST