On January 3, 2003, approximately 1815 central standard time, a Cessna 401 twin-engine airplane, N968JW, sustained substantial damage after it impacted a runway sign following a loss of control after the main landing gear collapsed during the landing roll at the Mc Allen Miller International Airport (MFE), near Mc Allen, Texas. The commercial pilot, sole occupant of the airplane, was not injured. The airplane was registered to Craftech Enterprises, Inc., of McAllen, Texas and operated by International Air Services of Edinburg, Texas. Bright night visual meteorological conditions prevailed, and a visual flight rules (VFR) flight plan was filed for the Title 14 Code of Federal Regulations Part 91 personal flight. The flight departed the Huejotsingo Airport, near Puebla, Mexico, approximately 1600, and was destined for MFE. The 2,462-hour pilot reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that the airplane experienced a partial loss of electrical power approximately 35 nautical miles south of Reynosa, Mexico (located 10 nautical miles south of Mc Allen). After crossing over Reynosa, he attempted to electrically extend the landing gear; however, the landing gear did not extend. While on a right downwind for runway 13 at MFE, the pilot manually extended the landing gear, but did not receive three green annunciator lights confirming the landing gear was extended and locked. Without radio communications, he was cleared to land via the air traffic control "steady green" light gun signal. During the landing roll, he felt the right main landing gear start to collapse and "gave it aerodynamic lift by deflecting the ailerons." Subsequently, the left main landing gear collapsed, the airplane exited the runway and struck a runway sign. The airplane spun 180-degrees and came to rest upright. According to an FAA inspector, who examined the airplane, the left wing had severe damage to the leading edge that penetrated the sheet metal between the spar angles. The lower side of the wing exhibited tears and wrinkles which included the trailing edge spar. The left aileron also sustained substantial damage. The FAA inspector further reported that the "left landing gear door panel was dented in a manner that confirmed the landing gear was extended and then collapsed." Examination of the airframe logbook revealed the main voltage regulator was replaced on December 21, 2002. The reason for the loss of electrical power was undetermined.