Critics lashed out at the government Friday for ignoring warnings that old train tracks were not designed to handle a new express train that derailed in northwestern Turkey, killing 36 people and injuring 81 others in one of the country's worst rail disasters.

The cause of the derailment was unclear, but government officials ruled out sabotage. The disaster was a major embarrassment for the government, which dismissed concerns raised about the high-speed train before service was inaugurated last month.

Paramilitary police Friday detained the train's conductor and his assistant for questioning, a police official told The Associated Press on customary condition of anonymity.

At daybreak, a crane lifted one of at least four flipped cars and loaded it onto a freighter train as railroad workers began repairing the tracks.

Engineers came forward after Thursday's accident saying they had warned the government numerous times that the old tracks along the Istanbul-Ankara line (search) could not handle the new high-speed cars.

A spokesman for Turkey's railroads, who refused to be named, said it was not clear how fast the train was going at the time of the crash. He said the speed limit near the crash site required the train to slow to 48 mph, from a previous speed limit of 78 mph.

Survivor Muhittin Anik said he went to the restroom five minutes before the crash and noticed that a speed indicator showed the train to be traveling at 85 mph.

Union leaders, opposition politicians and newspapers also said the government neglected warnings its showcase train was too fast for Turkey's antiquated railroad tracks.

"Serial murder," the daily Hurriyet newspaper said. "Express massacre," was the headline in Sabah.

Experts had called on the government to modernize the rail infrastructure before allowing the trains to travel. Aydin Erel, professor of engineering at Istanbul's Yildiz Technical University (search), said he warned the government as recently as July 14 that the tracks were not up to standard.

"Our infrastructure was not suitable for such speed," Erel said. "Our warnings were ignored."

The state-run rail authority rejected the criticism and insisted the lines were safe.

At least four cars overturned Thursday evening near the small, rural village of Mekece, with most of the damage in two cars that crashed into each other. Bodies lay near the tracks as searchers climbed on the overturned cars looking for survivors. Darkness hampered rescue operations, with soldiers searching the wreckage and treating the injured by flashlight.

"The train was a little fast going around the curves," said injured passenger Namik Kemal Ozden, lying in his hospital bed with his face bandaged. "There were vibrations. My cousin was sitting next to me, we hugged each other. The windows broke and we fell to one side. We could only understand what happened once we got out."

The crash marked a setback for Turkey's efforts to modernize its outdated rail services and for the government of Prime Minister Recep Tayyip Erdogan (search), who launched the high-speed line.

Erdogan canceled a trip to Bosnia and traveled to the disaster area by helicopter, where he faced angry survivors.

"Prime minister hear me! My husband is dead, he should never have ridden on that train!" a woman at a hospital shouted at Erdogan.

The new Istanbul-to-Ankara train, which cut travel time between the two cities from eight hours to five, was the first leg of government plans to renovate the antiquated rail system. The new train system was launched with a ceremony at which Erdogan wore a station master's cap, blew a whistle and then hopped on the train.

Much of Turkey's rail system dates back to the late 19th and early 20th centuries, and few lines have been renovated. Past governments have concentrated on building roads, neglecting rail lines.

There were conflicting reports of casualties, with the government crisis center, Health Ministry and Transportation Ministry earlier saying that between 128 and 139 people were killed. The ministries lowered the toll late Thursday to 36 without an official explanation.

Deputy Prime Minister Abdullatif Sener refused to explain the discrepancy, saying authorities were looking into it. He also rejected calls for the transport minister's resignation, saying it was too early to reach a conclusion.