The unemployment rate in construction dropped to the lowest April level in seven years as contractors added 32,000 workers to payrolls. The increase lifted industry employment to 6 million, the highest level since June 2009, according to a recent analysis of new government data by the Associated General Contractors of America.

“It is heartening that all categories of construction employers added workers, not only in April but over the past 12 months,” said Ken Simonson, the association’s chief economist. “Moreover, contractors have been adding to workers’ hours as well as hiring more employees.”

Construction employment totaled 6 million in April, a gain of 189,000 or 3.3% from a year earlier, while aggregate hours worked rose even more—up to 3.8%, Simonson noted. Residential building and specialty trade contractors added a combined total of 13,100 workers in April and 107,900 (5.0%) over 12 months.

Nonresidential construction—building, specialty trades and heavy and civil engineering contractors—grew by 18,600 employees last month and 81,300 (2.2%) since April 2013.

“There is a limit to how much overtime workers can put in, and companies will be seeking to expand employment even faster if the volume of projects continues to grow,” Simonson added. “But the huge drop in the number of unemployed former construction workers may make it harder to keep adding employees.”

The unemployment rate for workers actively looking for jobs and last employed in construction declined from 13.2% a year earlier to 9.4% last month. Simonson noted that the unemployment rate for construction workers had fallen by more than half since April 2010, when it reached 21.8%. During that time, the number of unemployed workers who last worked in construction declined by 1.1 million, but industry employment increased by less than 450,000.