WAUSAU, Wis. (CBS 58) -- A preliminary report from federal investigators found a failure to switch fuel tanks caused the plane carrying Republican candidate for governor Tom Tiffany to make an emergency water landing last month.

The National Transportation Safety Board (NTSB) issued its early findings, and it cited a conversation the plane's pilot, Leonard Boltz, had with an aviation mechanic following the crash.

"[The mechanic and the pilot discussed the accident," the report read. "During which the pilot said the loss of engine power was
due to his delay in switching fuel tanks and not turning on the electric fuel boost pump."

Tiffany and Boltz were able to make an emergency landing in Lake Wausau when the plane lost power on a flight back from Antigo on Sept. 12.

The plane was substantially damaged, but Tiffany and Boltz escaped with minor injuries. Both men were able to get out of the plane and swim to shallow water before first responders arrived to rescue them.

An inspection of the plane found the left main tank was empty while the right main tank and auxiliary tanks were full of fuel.

The report noted Boltz reported that as he approached the airport in Wausau, he extended the landing gear and observed a "higher-than-normal engine exhaust gas temperature (EGT)."

"According to the pilot, the higher-than-normal engine EGT reminded him to switch fuel tanks," the report read. "He selected the right fuel tank and advanced the mixture and throttle levers to the full forward position, but the engine did not respond."

At that point, Boltz told investigators he prepared for a water landing. The impact caused significant damage to the plane's fuselage, left wing, left aileron and engine mount.

The report noted its information at this stage is preliminary and still subject to change.