SANTA FE, N.M. (AP) — The New Mexico Legislature has approved funding to help shore up a giant, man-made cavern in southern New Mexico that is on the verge of collapse. The House of Representatives voted unanimously Monday to use a portion of excise taxes paid on vehicle sales to underwrite as much as $30 million in spending on the problem over the next three years. GOP Gov. Susana Martinez has until Thursday morning to veto or approve the measure. Experts are painting a dire picture about the impending collapse of the giant cavern under a highway interchange that serves as a gateway to southern New Mexico's oilfields and two national parks. The cavity was left by the extraction of a salt formation underneath the edge of Carlsbad.