BILLINGS, Mont. — A Minnesota-based agriculture company was fined $211,000 by federal safety regulators who said Wednesday it had repeatedly failed to ensure workers weren’t exposed to grain-dust hazards in Montana.

CHS Inc. was cited by the Occupational Safety and Health Administration for 19 workplace safety violations at grain elevators in Cut Bank, Glendive, Denton and Valier. A company spokeswoman said CHS will challenge the violations.

Three were repeat violations, including failing to test the air quality in work spaces for potentially explosive grain dust, hazardous gases or lack of oxygen, regulators said.

“When an employer sends their employee into a confined space, they must ensure the atmosphere is safe to breathe,” said Jeff Funke, OSHA area director. “We’re always disappointed when we find repeat violations. That means the employer has stated they’ve corrected these hazards — and now we’ve found them again.”

The dollar amount of OSHA penalties are increased five-fold for repeat violations by large companies, Funke said.

CHS, based near St. Paul has 15 days to either contest the penalties, pay them or request an informal conference with regulators in hopes of the reducing the amount.

Spokeswoman Lani Jordan said in an emailed statement that the company was disappointed by the severity of the allegations.

“We continually assess our facilities, our work practices and our safety training. CHS is proud of its excellent safety performance record in all of our operations, including those in the state of Montana,” Jordan wrote.

The company employs 10,000 people in the U.S. and abroad and had 2013 revenues of almost $45 billion.

Dust from grain in elevators is considered highly combustible and can be more explosive than coal dust, Funke said.

Fourteen of the violations alleged against CHS were classified as serious, meaning there was a substantial probability of a worker death or injury.

A CHS worker was killed in Kansas in 2010 when he fell into what regulators said was an inadequately protected grain bin.

The company agreed to pay $40,000 for two safety violations that federal officials said contributed to the accident, according to details of the case provided by OSHA.