Prices of commercial properties in the United States rose 4.1 percent in December, Moody’s Investors Service said Monday, further feeding the debate over whether the sector’s unpredictable crash has passed or still lies in the cards.

It was the largest month-to-month increase in the 10-year history of the Moody’s/REAL Commercial Property Price Index, and marked the second consecutive month of price gains reported by the credit ratings agency. Add to that the fact that transaction volume rose more than 75 percent in December from the previous month, and it’s easy to feel optimistic.

The ratings agency said there were 716 transactions in December totaling $9 billion. The dollar value of the deals was up more than 100 percent from November. It was also the first and only month in 2009 that the year-over-year dollar volume change was in positive territory, at nearly 5 percent, the company said.

But, Moody’s cautioned that it’s too early to determine if the recent increases signal an upswing from the price floor or simply reflect the volatility of a market in transition.

“Two months of positive returns and one month of higher transaction volume does not allow us to discern a trend just yet, particularly in light of the fact that year-end commercial real estate activity can distort the true condition of the markets,” the report said, noting that December often reveals a race to close deals by both buyers and sellers before year-end.

Looking at the individual commercial sectors, three of the four major property types saw value gains in the fourth quarter of last year. Offices produced the largest return, at 7.9 percent. Prices on apartments rose 7 percent and industrial properties increased 5.6 percent. Retail values, however, declined 1.5 percent for the quarter.

The quarterly returns represented a significant improvement, but for the year, all property sectors recorded hefty double-digit declines around the -20 percent mark.

Moody’s noted that overall, commercial property prices are down 29.2 percent from a year ago, 39.8 percent compared to two years ago, and 40.8 percent from the peak in October 2007.

Nick Levidy, managing director at Moody’s, said “Although we are unable to conclude that the bottom to the commercial real estate market is here, we do believe that the period of large price declines is over. We will need to see data from the first few months of 2010 to develop a better picture of where things stand.”