Orlando, Florida (CNN) -- A federal hearing began Monday to determine whether SeaWorld Orlando should be charged with a willful violation in the 2010 death of killer whale trainer Dawn Brancheau.
As witnesses took the stand inside the Seminole County Courthouse in Sanford, Florida, members of People for the Ethical Treatment of Animals, or PETA, demonstrated outside. Monday was the first day of the hearing, which will resume at 9 a.m. Tuesday and is expected to continue all week.
In February 2010, as park guests watched in horror, Brancheau, 40, was pulled into a SeaWorld pool and drowned by a 12,000-pound killer whale named Tilikum. Brancheau had been sitting on the Shamu Stadium's pool edge during a private show.
After a lengthy investigation, the Occupational Safety and Health Administration -- the federal agency that works to prevent workplace injuries -- cited SeaWorld of Florida in August 2010 for willfully endangering employees by not taking proper safety precautions.
"SeaWorld recognized the inherent risk of allowing trainers to interact with potentially dangerous animals," Cindy Coe, OSHA's Atlanta regional administrator, said in a statement.
"Nonetheless, it required its employees to work within the pool wall, on ledges and on shelves where they were subject to dangerous behavior by the animals," she said.
The citation said the park allowed its employees to work with Tilikum, a whale with "known aggressive tendencies" who was involved in the 1991 death of a trainer at a Vancouver, British Columbia, marine park.
The theme park did not provide barriers, decking, oxygen supply systems or other types of protection for the trainers, OSHA said.
SeaWorld spokeswoman Becca Bides disagreed, saying, "These allegations are completely baseless, unsupported by any evidence or precedent, and reflect a fundamental lack of understanding of the safety requirements associated with marine mammal care."
SeaWorld contested OSHA's findings and is presenting evidence to the OSHA Review Committee, a separate government agency, at this week's hearing in Sanford, northeast of Orlando.
OSHA Review Committee Administrative Judge Ken Welsch is presiding over the hearing, in which both sides are presenting evidence and witness testimony.
In his opening remarks on Monday, OSHA attorney John Black said SeaWorld allowed their trainers to take a calculated risk by working with killer whales that have the potential to cause harm or death to those who get close.
Trainers are required to sign a document that acknowledges that they have read the standard operating procedure manual and acknowledge the calculated risk. Black called the document a release waiver and argued that the park's training for the handlers was not enough.
SeaWorld's attorney said the handlers' training is only one component, noting that the animals are trained, too.
"It goes hand in hand," said Carla J. Gunnin Stone.
It's unclear if OSHA's attorneys will present surveillance video showing Brancheau's death. Her relatives have fought to keep it sealed.
U.S. District Judge Gregory Presnell on Thursday denied the Brancheau family's request to keep the tape from being released or used at the hearing.
"We cannot comment on what may or may not be presented (during the hearing), as that depends not only on our own attorneys but also on any rulings issued by the judge in the case," OSHA spokesman Michael Wald said.
Since the accident, SeaWorld has restricted all trainers from entering the water with killer whales until further notice, though Tilikum has returned in a theme park show called "One Ocean."