The 1,526-hour commercial pilot reported in the Pilot/ Operator Aircraft Accident Report (NTSB Form 6120.1), that he was returning the airplane after the completion of an extensive annual inspection. The pilot reported "topping off" the two main fuel tanks, performing a complete run-up, and finding no anomalies with the airplane's engine and flight controls. During the initial climb-out, while climbing through an altitude of 500 to 600 feet above ground level (agl), the engine lost power. The pilot reported that he immediately checked the mixture and using the primer was able to momentarily regain engine power. Once again the engine lost power and an attempt to restart proved unsuccessful. While descending, the pilot elected to turn the airplane left towards an open field located northeast of the departure runway. During the forced landing, the airplane struck the tops of several trees, coming to rest on the ground, facing the approach heading. There was no fire and the pilot was able to egress the airplane unassisted. Examination of the airplane by a Federal Aviation Administration (FAA) inspector, who responded to the accident site, revealed both wings separated from the fuselage, the propeller was detached, and the landing gear was broken off. The reason for the reported loss of engine power could not be determined. At the time of the accident, the weather was reported as wind from 200 degrees at 9 knots, gusting to 14 knots, 10 statue miles visibility, clear skies, with temperature of 81 degrees Fahrenheit, dew point of 61 degrees Fahrenheit and an altimeter setting of 29.83 inches of Mercury.