On July 24, 2004, about 1500 eastern daylight time, a Piper PA-28-140, N6139J, was substantially damaged during a forced landing, following a loss of engine power after takeoff from Somerset Airport (SMQ), Somerville, New Jersey. The certificated flight instructor and student pilot were seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight conducted under 14 CFR Part 91. The flight instructor reported that due to her injuries, she did not have any recollection of the day that the accident occurred. According to a Federal Aviation Administration (FAA) inspector, the flight instructor was providing an introductory flight to a prospective student. As the airplane began an initial climb from runway 12, a witness at the airport heard the engine sputter. The airplane then began to descend and turn right, away from a wooded area at the departure end of the runway. However, the left wing struck a tree, and the airplane came to rest upright in an adjacent field. The wreckage was examined by a representative from the engine manufacturer, under the supervision of the FAA inspector. During the examination, approximately 5 ounces of fluid were recovered from the carburetor bowl. About one-third of the fluid was consistent with water, and the remaining fluid was consistent with 100 LL aviation gasoline. Several droplets of fluid were also recovered from the fuel strainer. Some of the droplets were consistent with water. The FAA inspector further stated that the airplane was last fueled two days prior to the accident, and remained parked outside until the accident flight. During that time, the airport experienced periods of heavy rainfall.