Who blocked the SEC's investigation?

Mr Kucinich, chairman of the Domestic Policy Subcommittee in the House of Representatives, told BBC Radio 4's Today programme that the SEC "did not do its job". He said:

"The fact of the matter is there were smoke signals about this particular individual and his manner of investments for a couple of years in a number of places, including the US, and nothing was done.
"We cannot let this thing slide ... until we find out how long the government knew about it, what was known, when was it known and why was the SEC told [in 2006] to stand down in its investigation [of Stanford], apparently by another federal agency."

Timeline, News1, News2.