This is the latest move in a campaign to win pay of $US15 ($A19.70) an hour and unionisation for fast food workers by publicly pressuring McDonald’s.
The push began more than two years ago and is being spearheaded by the Service Employees International Union.
The burns and other hazards were detailed in complaints announced on Monday and filed with US Occupational Safety and Health Administration in recent weeks.
In a statement, McDonald’s said franchisees were committed to providing safe working conditions and it would review the allegations.
A Labor Department representative confirmed the complaints were received by OSHA but said the agency didn’t discuss ongoing investigations