For at least the second time this summer, gasoline fumes are believed to be the culprit in a serious boating incident in a park. Five people were injured in an explosion aboard a boat at Lake Mead National Recreation Area.

At about 6 p.m. Thursday evening, authorities were notified of a boat explosion at the Callville Bay Marina, on the north side of Lake Mead.

National Park Service rangers and firefighters responded, along with personnel from the Clark County Fire Department.

According to park spokesman Anthony Munoz,

Seven people from Las Vegas were aboard when the explosion happened. Five were injured; three were transported by ambulance to University Medical Center, two declined treatment. Injuries included burns and abrasions.

Forever Resorts marina employees provided first aid to the injured and protected visitors by moving the boat away from the marina.

While the exact cause of the incident remains under investigation, investigators suspect that this may have been caused by a build up of gasoline fumes.

Earlier this summer, a boat was destroyed by a fire at Glen Canyon National Recreation Area when the boat owner started the engine shortly after refueling the boat—even though he could smell gasoline fumes.

There's no indication in the latest incident at Lake Mead that the boat operator acting improperly. Even so, both situations offer a timely reminder that gas fumes can pose a definite hazard for boaters. Here are a few tips from the staff at Lake Mead to help prevent an explosion while fueling a boat:

• Close all hatches and other openings before fueling.
• Extinguish all cigarettes and other open flames.
• Turn off engines, all electrical equipment, radios, stoves and other appliances.
• Remove all passengers.
• Keep the fill nozzle in contact with the tank and wipe up any spilled fuel. Spilled fuel can turn into vapors.
• Open all ports, hatches and doors to ventilate after fueling.
• Run the blower on the boat for at least four minutes after fueling is completed.
• Check the bilges for fuel vapors before starting the engine.
• Make sure there is no odor of gasoline anywhere in the boat before starting the engine.