Coleman Nee (second from right) was Secretary of Veterans Services under Governor Deval Patrick and now serves as a the chief executive of Triangle Inc. Bill Brett/Globe Staff/File 2012

Last June, as employees at Triangle Inc. began organizing ahead of a possible vote to unionize, federal officials say their chief executive, Coleman Nee, delivered a straightforward but potentially unlawful message: Voice support for the union, and you could be fired.

The comment began a monthslong campaign of harassment, surveillance, and coercion by Triangle officials, according to federal investigators, who say they found evidence that the Malden nonprofit ran afoul of federal labor law in an alleged push to quash union organizing.

The National Labor Relations Board’s Boston office has now taken the rare step of issuing a formal complaint and scheduling a hearing before an administrative judge for Triangle officials to answer to the allegations.

The accusations against Nee, a former Cabinet secretary under Governor Deval Patrick, and other Triangle officials were sparked by complaints from four former employees, who charged they were fired for helping organize the roughly 175-member work force to unionize with SEIU Local 509.

“It was an injustice,” said Amy Banelis, 36, who was an employment specialist with Triangle, which trains and connects developmentally disabled people with employment opportunities.

Banelis was told in August that her job was being eliminated. “When you have certain individuals fired for organizing, folks are going to be scared. Triangle had sent a clear message by firing us that they essentially don’t want a union there,” she said.

Nee and five other Triangle leaders spent months “interfering with, restraining and coercing employees,” including repeatedly interrogating them about the union activities of others, according to a copy of the NLRB’s Feb. 28 complaint provided to the Globe.

It began in June 2017, when Nee, the state’s former secretary of veterans’ services, “told employees that if they told others that they supported the union, they could be fired,” according to the complaint.

The nonprofit’s director of human resources also repeatedly harassed employees, demanding they obtain a union authorization from her. Other officials also documented in employees’ performance reviews whether they were speaking to others about unionizing, according to federal officials.

Ultimately, Banelis, Joseph DiVincenzo, and Jim Kane were let go. The NLRB said their dismissals were an effort to “discourage employees from engaging in these or other concerted activities.” The NLRB did not include allegations leveled by a fourth former employee in the complaint, after determining that worker was a supervisor.

Triangle officials have until Wednesday to file an answer to the complaint, and a hearing has been scheduled for June.

Established in 1971, Triangle has more than 3,900 people enrolled in various programs and services during fiscal year 2017, when it had $10.2 million in revenue and $10.15 million in expenses, according to its most recent annual report.

Nee did not return calls to his cell phone and office Friday. But in a statement issued through spokeswoman Dot Joyce, nonprofit officials said they prefer to “amicably resolve the dispute.” They argued the employees were laid off in a bid to cut costs amid a budget deficit.

“Triangle is not anti-union,” the statement read, “and Triangle would prefer to devote its limited financial resources to providing services to disabled individuals.”

Peter MacKinnon — president of SEIU Local 509, which filed the initial allegations — said the union is open to negotiations, but says Triangle’s moves to date have had a “chilling effect” on any organizing.

“It’s one of the reasons why these workers wanted to form a union in the first place. They were scared of their management,” he said.

The NLRB said its policy is to encourage settlements. That means complaints often make up only a “small minority of the cases,” said William B. Gould IV, a Stanford law professor and former NLRB chairman.

“If a complaint is issued, it means the general counsel, who is the prosecutor of the board, has found enough cause to believe the allegations,” Gould said.

Of the nearly 20,000 unfair labor allegations filed with the board last fiscal year, only a fraction — about 6.5 percent — led to formal complaints, according to NLRB data. Most allegations are withdrawn or dismissed.

“I’m not hoping that Triangle fails,” said Kane, one of the former employees. “I hope the management changes, or changes its perspective. If that happens, there wouldn’t be a need for union organizing in the first place.”