There are signs the U.S. construction industry’s long-awaited recovery may be under way.

Employment levels grew in two-thirds of all states in December 2012 and half saw an increase in year-over-year employment, the Associated General Contractors of America said.

The figures from the U.S. Labor Department are the surest sign yet that construction’s six-year slump may be ending, said Ken Simonson, AGC chief economist.

“These results show that contractors are finding work in more parts of the country than they have for many months,” Simonson said. “Further gains appear likely but could be derailed if lawmakers do not keep debt markets operating normally.”

The most construction jobs were added in Nebraska; Washington, D.C.; Texas; Hawaii; and Washington state in December. For the year, the most jobs were added in Texas, California, Washington state and Arizona.

“Construction spending has been rising for two full years but contractors have been cautious about adding workers until they knew the upturn would last,” Simonson said. “In 2013, both residential and private nonresidential construction should rise enough to offset a further slowdown in public work, and contractors will be looking for more workers.”

Stephen E. Sandherr, the association's chief executive officer, said industry workers should not expect a quick rebound, however.

“There is a growing sense of optimism within the construction community that the worst is over,” he said. “At the same time, however, just because the worst is over doesn't guarantee that conditions are going to get significantly better anytime soon, especially if Washington can't find a way to address out-of-control entitlement spending that is making it increasingly difficult to invest in aging infrastructure and other important construction programs."