PORTLAND – Construction workers gathered at the gates outside an oil rig project Thursday morning to protest Cianbro Corp.’s decision to hire up to 60 welders from Canada.

Peter Vigue, president and chief executive officer, defended the company’s actions. He said Cianbro sought approval to hire the Canadian workers because there were not enough certified welders in Maine.

Currently, Cianbro has forwarded the names of 21 Canadian welders for visas allowing them to work on the oil rigs, he said. State and federal officials have approved the hiring of up to 60 Canadian welders, he said.

Altogether, there are 602 Cianbro workers and another 229 workers hired by subcontractors building two massive oil rigs in Portland Harbor.

The rigs, dubbed Amethyst 4 and Amethyst 5, are not designed for oil production, but for exploration. They are contracted to the Brazilian oil company Petrodrill, for work off South America.

“This is a major project for our company and the state of Maine. It’s a tremendous challenge and at the same time an opportunity. The project is extremely complex and technical and we’re succeeding to be sure,” Vigue said.

The biggest obstacle to the project has been finding Lloyd’s-certified welders who are qualified for the project, Vigue said. Cianbro found a group of qualified welders in New Brunswick and Nova Scotia, he said.

Unions have accused Cianbro of simply seeking to hire workers who are not represented by labor groups.

Vigue denied that, saying some of the subcontractors utilize unionized work forces. Cianbro’s work force is not represented by unions because that’s what the workers want, he added.

Pipe welders on the project are paid an average of $18.71 an hour and also receive full benefits, Vigue said.