At least three people were killed and two others were wounded in a shooting at an In-N-Out Burger in Twin Falls, Idaho, on Saturday, the authorities said.

The Twin Falls police received a call around 2:30 p.m. local time about an active shooter inside the dining area at the In-N-Out Burger restaurant on Blue Lakes Boulevard, said Josh Palmer, a city spokesman.

The suspected shooter is dead, the police chief in Twin Falls, Matthew Hicks, said during a news conference on Saturday.

It was not immediately clear if the gunman was among the three fatalities or in addition to them. It was also unknown how the shooter died.

The number of victims is “expected to be higher,” Mr. Palmer said.

The events leading up to the shooting were not immediately known.

“We have literally hundreds of people that were in some way, shape or form in the area of this restaurant at the time,” Chief Hicks said. “This is an exceptionally chaotic scene, on a Saturday afternoon here in Twin Falls, at one of the busiest locations in all of southern Idaho.”

By the evening, the police were working with a hospital, St. Luke’s Magic Valley Medical Center, to “ascertain the exact number of fatalities,” Chief Hicks said.

The hospital posted a statement asking people to avoid the area around the hospital. Officials later added that the hospital was not accepting visitors.

“Please avoid going to St. Luke’s Magic Valley unless it is an emergency,” the statement said. “The Emergency Department remains open.”

The In-N-Out Burger had opened on Friday, drawing crowds, including some who had camped outside ahead of the morning opening, according to local station KMVT-11. Denny Warnick, the chief operating officer for In-N-Out Burger, told the station it was the state’s fourth location.

Mr. Warnick said in a statement on Saturday that restaurant officials were “heartbroken.”

“Our prayers go out to our customers, our associates, and all of their families,” he said. “We are working with the Twin Falls Police Department to assist in the ongoing investigation.”

The restaurant is in a popular shopping area with chain restaurants and big box stores near Interstate 93 and a bridge that takes drivers into Twin Falls.

This is a developing story.