ANCHORAGE, Alaska — Five people who drove onto Cook Inlet mudflats and got stuck were rescued by helicopter Saturday night as tidewater rose around a sport utility vehicle where they had taken refuge.

Rescuers could not immediately reach them on the ground because they had driven onto a Joint Base Elmendorf-Richardson firing zone where potentially live ordnance could have exploded, the Anchorage Daily News reported Monday.

The incident began early Saturday night. A husband and wife drove an SUV along Route Bravo Road on base, Master Sgt. Richard Matteson, an Air Force battalion chief with the 673rd civil engineering squadron, said in a written statement released by the Alaska National Guard.

“People will go back there in their 4-by-4s and kick up a lot of dust,” Guard spokesman Sgt. Edward Eagerton said. “You are not supposed to deviate from the roads and just kind of go do your own thing. Each of those areas are controlled ranges, and in order to enter those areas, you have to get permission from range control.”

He did not know if they were civilians, contractors or members of the military, but they had permission to be on base, Eagerton said.

Their SUV became stuck in mud, and they put out a Facebook message calling for help, said Matteson, the rescue incident commander.

Friends responded in another SUV and brought along their 5-year-old boy. The second SUV also became stuck, though not as far from shore.

By 8 p.m., a nearly 30-foot high tide had moved in.

“The occupants of the first Jeep abandoned their vehicle when the rising tide submerged it,” the National Guard account said. “They took refuge in the second Jeep, stuck further back in the mud.”

Matteson and security forces responded but hesitated crossing “a munitions impact area” that was under water.

The tide rose to the doors of the second SUV, and water flooded in, Matteson said. The people were wearing jeans and T-shirts.

“We thought about leaving them in the vehicles for the night until (the disposal team) could clear a route, but the 5-year-old boy began showing signs of hypothermia, and we knew we had to get them out of there,” Matteson said.

The Alaska Air National Guard reached the scene with a Pave Hawk helicopter just after 11 p.m. and hoisted up the five people. They were examined at a hospital and released.