Inspectors have found 21 more cracks in welds or steel structural pieces on an elevated subway line that had a section collapse in May, killing 26 people, officials said Wednesday.

Studies on the fallen section found the failure was caused by construction defects like poor welds and missing connection studs as well as bad design. The newly discovered cracks are on other parts of the line that didn’t collapse.

The inspection is only about one-third complete, so more such defects may be uncovered.

Outside inspectors have been invited in as part of efforts to re-open and reinforce the line, including some from the Autonomous University of Nuevo Leon.

Telecom and construction magnate Carlos Slim has said his Grupo Carso’s construction subsidiary will pay the cost of rebuilding the span that collapsed and reinforcing other parts of the elevated line to meet higher standards in a city plagued with severe earthquakes.

Earlier this year, Mexico City prosecutors announced criminal charges against 10 “individuals and companies” for construction and design defects.

In the case of the companies involved, prosecutors have said the goal of the criminal charges is aimed at making them pay for or repair damages both to the subway and the victims. The charges are for negligent or involuntary homicide, damages and causing injuries.

Inspections of the collapsed section cited poorly welded, badly located and completely missing studs that were intended to join steel support beams to a concrete layer supporting the track bed.

Prosecutors also cited bad welds in the steel beams underlying the concrete track bed that either failed to adhere or split. Steel struts intended to stiffen the metal beams were too short or not properly attached, and the elevated line was not designed with enough of a safety margin.

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