The Securities and Exchange Commission

has begun probing issues involving collateralized debt obligations related to the subprime-mortgage market, according to published reports Tuesday.

SEC Chairman Christopher Cox, answering a question about market transparency of CDOs at a House Financial Services Committee hearing, said the SEC's enforcement division has opened "about 12 investigations" pertaining to CDOs and collateralized loan obligations, (CLOs),

The Wall Street Journal

said online.

CDOs are at the core of

the recent mess at

Bear Stearns

(BSC)

hedge funds.

Additionally, the SEC enforcement division also has opened an investigation into matters regarding the Bear Stearns hedge funds, sources familiar with the matter say, according to the

Journal

.

In a statement late Tuesday, Bear says it

doesn't believe it will have to bail out its High-Grade Structured Credit Strategies Enhanced Leverage Fund, a more highly leveraged hedge fund also struggling, says a report by

Bloomberg

.

Shares of Bear Stearns closed Tuesday's regular session up a quarter to $139.35.