Traffic Control Errors Caused Spain’s Deadly Train Crash, Official Says The transport minister said a judge would investigate controllers’ actions, including authorizing a train to proceed at high speed though another was stalled in front of it.

Rail traffic controllers gave the green light to a train racing at about 100 miles per hour toward a stopped train this week, precipitating the crash that killed at least 69 people and shook Spain’s confidence in its rail system, the transport minister said on Friday. A judge will investigate several “inexplicable” errors on the part of the controllers, including instructing the moving train to proceed at high speed despite a technical problem, the minister, Óscar Puente, said at a news conference, giving the most detailed account yet of what caused the crash on Wednesday. He said he had no intention of resigning, despite mounting pressure after the second deadly train crash in under a year.

For 17 minutes, controllers at an operations center in Madrid were able to see on “screens and systems” that one train was moving while the other stood still, Mr. Puente said. “Those in the control center had full visibility of what was happening,” he said, but did nothing to stop it.

“That’s why it has to be investigated,” he added. He said it would fall to independent investigators and “a judge to receive the appropriate explanations so we can understand how this could happen.”The crash was the deadliest in Spain in more than a decade. In addition to those killed, dozens of passengers remain hospitalized, 17 of them in intensive care, officials have said.

The rail traffic center in Madrid had to take control of train movements on Wednesday after an aging, automatic safety system, which normally controls signals, shut down for part of central Spain, the government has said.

While questions have arisen about the age and operability of that system, known as LZB, Mr. Puente defended it, saying “it was every bit as solid and reliable” as a new system set to replace it next year. The new system, he said, is needed to bring Spain more in line with other European countries and to satisfy new industrial manufacturing requirements.

He said the system had gone down roughly 170 times this year, a figure he described as consistent with previous years and “well within standard European figures.”Many of those outages, he said, were related to vandalism, cable theft and construction on the tracks.

Mr. Puente said the operations center was properly staffed and funded, despite train worker unions’ claims to the contrary. Even so, he added, the government, which faces elections on Nov. 29, is preparing “a package of immediate measures” to avoid more failures by giving operators “the most advanced technology” to minimize risk.

When the system went down at 8:31 a.m. on Wednesday, all trains in the vicinity automatically stopped. That left it up to a backup automated system and controllers to take charge of the signals, in communication with train operators.

Under those conditions, Mr. Puente explained, one train is not permitted to enter a sector of track already occupied by another train. The problem, he said, was that when the main automated system went down, two trains stopped in the same block of track south of Toledo, in central Spain.

Rail regulations say that “the trailing train must not move until the forward train has departed,” Mr. Puente said. But at 8:36 a.m., he said, controllers told the trailing train, operated by the state-owned company Renfe, to resume its journey.

Regulations also stipulate that in such situations, trains should not travel faster than about 25 miles an hour, so that conductors can stop if they see something ahead on the track. Instead, he said, controllers instructed the driver to return to normal speed, which is up to 124 miles an hour on that stretch.

Mr. Puente said the operators only authorized the forward train, operated by the company Iryo, to proceed at 8:41 a.m., turning the signal ahead of it green.

But the train couldn’t restart. At 8:48, he said, its driver contacted the control center to report that the train was unable to move.

“The center received the message,” Mr. Puente said, “but took no action.”Mr. Puente said that because the signal ahead of the Iryo train had turned green, the traffic signal behind it also did so, indicating that the tracks were clear, though the Iryo train had not moved. The Renfe train barreled past that green light before the collision.

“Why, if it was possible to act and there was time to do so, was nothing done? I have absolutely no idea,” Mr. Puente said on Friday. “That is one of the things the investigation will have to clarify.”