A Douglas DC-4 airplane has crashed into a river in Fairbanks in U.S. state of Alaska on Tuesday, authorities said.

First responders were conducting an "active rescue" Tuesday morning after the plane crashed in the area of the Tanana River in Fairbanks, according to local officials.

Clint Johnson, Alaska chief of the National Transportation Safety Board, said it was not clear how many people were on the Douglas DC-4 when it crashed around 10:30 a.m. shortly after departure south of Fairbanks International Airport.

"We acknowledge the ongoing situation involving the Douglas DC-4 aircraft on the Tanana River near Kallenberg Road," the airport said in a statement. "Alaska State Troopers are actively leading the response and we are cooperating with them."

A spokesman for Fairbanks International Airport urged the public to avoid the area.

Alaska State Troopers, along with local, state and federal agencies, were responding to the crash near Kallenberg Road on Tuesday morning.

A witness said he heard a loud explosion and saw a plane overhead with an engine on fire, according to a report by the Anchorage Daily News.