Full sawtooth crashes in high temperature plasmas have been investigated on the Tokamak Fusion Test Reactor ͑TFTR͒ ͓Plasma Phys. Controlled Fusion 33, 1509 ͑1991͔͒. A strong asymmetry in the direction of major radius, a feature of the ballooning mode, and a remaining mϭ1 region after the crash have been observed with electron cyclotron emission image reconstructions. The TFTR data is not consistent with two-dimensional ͑2-D͒ models; it rather suggests a three-dimensional ͑3-D͒ localized reconnection arising on the bad curvature side. This process explains the phenomenon of fast heat transfer which keeps the condition q 0 Ͻ1.