URDA, Spain — Was Spain’s second major train collision in nine months caused by human error, or did it stem from deeper problems in its once- vaunted high-speed rail network? Transport Minister Óscar Puente has blamed a traffic controller’s poor judgment for much of what went wrong in Wednesday’s collision in Toledo province, which killed at least 69 people. Railway unions have pushed back, citing deteriorating working conditions. They say too few controllers are handling growing workloads, making it increasingly difficult to ensure the safety of millions of passengers. As the country sought answers on Friday, police with sniffer dogs continued searching the wreckage. Regional authorities warned that the death toll could rise. It was the second major crash on the Madrid-Seville line this year. In January, more than two hours farther south along the route, a train derailed and struck another traveling in the opposite direction, killing 46 people. That crash remains under investigation. “It is unacceptable that a country like Spain with such a strong high-speed railway has two ac