Authorities said Wednesday that a 6-year-old girl suffered a severe electric shock and that a man who tried to help her also was hurt in an incident at MGM National Harbor in Oxon Hill, Md.

Prince George’s County Fire Department officials said the girl suffered injuries that are “consistent with an electrocution.” She was taken to a hospital in critical condition, according to Assistant Fire Chief Alan Doubleday.

The man, a security officer at the MGM facility, suffered injuries that weren’t considered life-threatening, officials said. The incident occurred Tuesday just before midnight.

Authorities said an initial investigation found that two children were touching a rail that was energized with lights and is near a fountain at an outdoor part of the resort.

Doubleday said that it is believed that the girl received an electric shock and that the security guard pulled her off the rail in an attempt to rescue her. Two other people, an adult and a child, also were hurt, but their injuries weren’t believed to be life-threatening. Doubleday said people took them to a hospital.

On Thursday, Prince George’s County Fire officials said in a Twitter message that the investigation was ongoing and that the girl’s condition was unchanged and she was still in critical condition in the hospital.

Doubleday said that when firefighters arrived, a Prince George’s police officer was performing CPR on the girl, who was in cardiac arrest.

“The police officer did an amazing job,” he said. He said the officer, along with firefighters, did “regain a pulse on the child.”

“We wish the best for the child,” the assistant fire chief said.

He said that the county’s department of permitting and inspections is being contacted to do an electrical inspection and that the fire marshal’s office will gather evidence as part of its investigation.

MGM National Harbor is a resort with dining, entertainment, stores and a casino near the Potomac River.

In a statement, Malik Husser, a spokesman for the MGM property, called it a “horrible accident” and said “we are heartbroken.”

“We offer our support and prayers for the family,” he said. MGM is cooperating with investigators, he said, and the area where the incident occurred is closed to the public as “investigators and our engineers conduct a comprehensive assessment of the situation.”

Husser said the incident occurred in Potomac Plaza, an outdoor patio area on the west side of the resort. He said it was not related to construction on MGM’s second level.