Four people were killed Wednesday when a small airplane crashed just north of Anchorage, the fire chief said.

The Cessna 172 crashed shortly after 9 a.m. near Chugiak, a bedroom community about 20 miles north of downtown Anchorage, fire Chief Denis LeBlanc said.

The plane was carrying four people when it crashed under unknown circumstances, Federal Aviation Administration spokesman Allen Kenitzer said in an email.

Few other details were immediately released, including whether the plane was taking off or landing when it went down.

Clint Johnson, head of the Alaska division of the National Transportation Safety Board, said an investigator was en route to the site.

Police said the crash happened near a dog mushing trail.

LeBlanc said the fire was contained to the site and didn't spread to nearby woods.

Police got a call from a citizen who said they thought they heard a plane crashing near a road.

"A few moments later, they observed smoke," Anchorage police spokeswoman Jennifer Castro said.