The collision of big rigs damaged a vital portion of the north-south artery just south of the intersection of I-5 (Golden State Freeway) and SR14 (Antelope Valley Freeway) and sparked a devastating inferno inside the tunnel, generating intense heat, estimated at up to 1500 degrees. The heat caused concrete to crack and melt, pulling away from the tunnel's steel reinforcement bars. Inspectors took core samples of concrete and steel to examine microscopically in order to determine the extent to which they might have been weakened. Structural analysis of these samples assisted Caltrans engineers in determining the extent of the damage.