JANESVILLE, Wis. (AP) — Federal investigators are expected to begin their work Wednesday at the site of a fatal plane crash in southern Wisconsin.

Two people died Tuesday when a small plane crashed shortly after takeoff from the Southern Wisconsin Regional Airport in Janesville. Authorities say the plane went down in a swampy area and was partially submerged in ice and mud.

Janesville Fire Chief Ernie Rhodes says the plane hit some trees on the way down, tearing off the wings.

First responders tried to reach the crash site with all-terrain vehicles, but couldn’t get through the deep snow and downed trees.

Rescuers used an airboat, launched upstream at Happy Hollow Park, and reached the plane about 10 a.m., approximately 45 minutes after it crashed, the Janesville Gazette reported.

Janesville Fire Chief Ernie Rhodes says the plane was in contact with the airport tower for a very short time and reported a problem, but the nature of the problem was not known.

Investigators believe the pilot was trying to return to the airport when the plane, described as experimental, crashed.

The victims have not been identified.