After the Federal Reserve committed to buy up even more toxic mortgages at its bi-monthly meeting, interest rates on long-term U.S. mortgages dipped back down under the 5 percent mark again, according to mortgage giant Freddie Mac Thursday.

“Following the March 18th Federal Reserve monetary policy statement, which announced further spending initiatives on financial assets, long-term bond yields plummeted,” said Frank Nothaft, Freddie Mac vice president and chief economist. “Yields on 10-year Treasury bonds fell by about a half percentage point after the announcement, marking the largest one-day decline since October 20, 1987.”

The average rate on a 30-year fixed rate loan dropped to 4.98 percent, excluding fees, during the week ended March 19, 2009, down from 5.03 percent the previous week. The current rate is just slightly above the all-time low from the week of January 15, 2009 when it hit 4.96 percent. One year ago, the average rate was 5.87 percent.

“Long-term mortgages followed bond yields lower for the second week as reports of slower industrial production suggested that business spending might ease this year,” Nothaft also pointed out. “Output at factories declined for the fourth consecutive month by 1.4 percent in February driven by declines in computers and machinery and experienced the largest 12-month drop since June 1975. In addition, factory capacity utilization slumped to 70.9 percent, matching the lowest rate since records began in January 1967.

Rates on the 15-year fixed rate mortgage loan fell to 4.61 percent, from 4.64 one week earlier. According to Freddie Mac records, the current rate is an almost six year low. Last year at this time, the average rate was 5.27 percent.

Interest rates on one-year adjustable rate mortgages however, increased in the latest week, growing to 4.91 percent from 4.80 percent. During the same week of 2008, the average rate was 5.15 percent.