A 9-year-old girl died on Thursday night while using a wave pool at Hersheypark in Pennsylvania, where lifeguards tried rescuing her after seeing her in distress, park officials said.

It was not clear whether the girl, whom the authorities did not name, had drowned or had experienced another issue.

The wave pool, which is known as The Shore and holds 378,000 gallons of water, remained closed on Friday. It gradually deepens from zero to six feet, according to the amusement park’s website.

John K. Lawn, the chief executive of Hershey Entertainment & Resorts, said in a statement on Thursday night that safety was the park’s top priority.

“Our hearts break for this child and the child’s family,” Mr. Lawn said. “In the coming days, we will conduct a thorough internal review and cooperate fully with the authorities.”

A person who was visiting the park at the time told the television station WGAL in Pennsylvania that they saw lifeguards performing CPR on the girl to no avail.

The park said that the girl was rushed to Milton S. Hershey Medical Center in Hershey, Pa., but could not be saved.

The police department in Derry Township, Pa., which Hershey is part of, said in a statement on Friday that it was assisting the amusement park and the Dauphin County Coroner’s Office with a review of the girl’s death.

The coroner’s office and county did not immediately respond to a request for comment on Friday.

David Sassaman, a spokesman for the Hershey Volunteer Fire Department, said that the agency was briefly dispatched for a medical assistance call to the park on Thursday night, but that request was canceled.

Hersheypark, the largest amusement park in Pennsylvania, has its own team of emergency medical technicians.

Park officials said on Friday that at the time that the girl died, more than 100 trained lifeguards were on duty in the water park, which is called The Boardwalk and is included with amusement park admission.

Ten of them were stationed at the wave pool, according to the park, which said that those lifeguards are trained in deepwater lifeguarding, basic life support, automated external defibrillator, or A.E.D. use, supplemental oxygen support, CPR and first aid.

The park also said that complimentary life vests are available to all guests. It did not say whether the girl was wearing a life vest.