PORTLAND – Maine builders are increasingly turning to immigrant labor because of a shortage of skilled workers.

Latin American migrants who have long been coming to Maine to help harvest crops are now becoming a presence at construction sites because of a lack of Mainers trained in drywall installation, carpentry and other skilled trades.

The average Maine construction worker is 48 years old, according to the Associated Constructors of Maine. Despite paying competitive wages, the industry is struggling to attract young people.

The practice of bringing Latin American construction workers to Maine has led to a pair of notable incidents in the past month in Maine as the federal government renews debate over a framework for immigration reform.

On April 1, four Mexican drywall installers found to be in this country illegally were arrested near a job site in South Paris. Three weeks later, a dozen Latin American drywall installers working on a condominium project in Portland failed to return to the job after offering interviews to the media.

More than 8,000 construction projects were under way in Maine last year, with an estimated value of $2.4 billion, according to the Associated Constructors of Maine.

No one tracks how many of these projects use migrant labor. But the trend comes as no surprise to Scott Tompkins, deputy director of the constructors group.

“It’s a continuation of the staffing shortage some of these companies have had for quite a while,” Tompkins said.

Roland’s Drywall of Sabattus, which is working on a condominium project in Portland, paid full-time workers on the condo project from $18 to $25 an hour, said Tony Gravel, the drywall project’s foreman.

Despite the good pay, his company can’t find enough local, trained drywall hangers.

The shortfall lead Roland’s Drywall to work with a labor supplier in New Hampshire to find experienced, Latin American construction crews.

Tompkins’ group is working with community colleges and vocational high schools to interest young people in the trades.

It’s also in the midst of a television advertising campaign to burnish the industry’s image. The campaign is battling two demographic trends: The demand for construction workers is growing in Maine, while the median age of the work force is rising.