U.S. worker productivity declined in the first three months of the year as labor costs jumped, reflecting a slowdown in growth.

The Labor Department says productivity, which is the amount of output per hour of work, fell at 1.9 percent rate in the first quarter. Productivity dropped at a 2.1 percent rate in the final three months of 2014.

Labor costs surged at a 5 percent rate in the first quarter, after having increased 4.2 percent in the fourth quarter.

The drop in productivity and rise in labor costs are signs of nearly flat economic growth in the first quarter, when overall growth was hammered by harsh winter weather and falling oil prices that hurt energy firms.

Still, economists say quarterly changes in productivity and labor costs are extremely volatile.