Officials in Russia say a train crash that killed at least 26 people and injured at least 50 late Friday may have resulted from an attack.



Prosecutors said Saturday they have begun a criminal investigation that could result in terrorism charges, but did not identify suspects. Investigators near the town of Bologoye are looking for clues into what caused the deadly incident on the Nevski Express high-speed luxury train.



Rescue workers are sifting through the wreckage in search of 18 missing people and have said that the death toll is likely to rise.



Russian news agencies report a small crater was found at the site of the wreck. Witnesses said they heard an explosion.



Sergei Shoigu, Russia's emergency situations minister, described the situation during a live broadcast from the national crisis response center in Moscow.



Shoigu says that at least 96 people have been injured. He says everyone that has been injured has been evacuated to a hospital, those with more serious injuries will be taken to Moscow and St. Petersburg.



Russia's health minister, Tatyana Golikova, details some of the injuries that passengers have received.



She says some suffer from head injuries, broken bones , internal bleeding and collapsed lungs.



Russian Railways president, Vladimir Yakunin, says that the cause of the derailment has yet to be determined, but sabotage has not been ruled out.



Russia's interior minister, Rashid Nurgaliev, says that the Kremlin has taken all measures to ensure that order is maintained and the accident is being investigated fully. He says that on Friday Night, a special investigative team was dispatched to the scene, including officers trained to investigate serious crimes.



Russian President Dmitri Medvedev echoed the seriousness of the situation, saying the government is doing everything it can to help people and also called on the police for assistance.



Mr. Medvedev says the government has taken all measures to ensure that order is maintained and that the country needs the police to help with the tragedy.



Officials with Russia's domestic intelligence service, the FSB, have yet to comment on whether the derailment was caused by terrorism.



Russian trains have been the targets of bombers in the past. In 2007, a blast derailed a Nevski Express train, injuring 27. Officials arrested two residents of Chechnya in that incident. In 2003, a suicide bomber attacked a commuter train near the Russian republic of Chechnya, killing 44.



Analysts say that terrorism has been a major concern in Russia since the fall of the Soviet Union in 1991. Chechen rebels have clashed with the government in two wars. Violence connected to the conflicts in the Caucasus has also erupted in other parts of Russia, including the Moscow subway attacks in 2004.



The accident is Russia's worst train calamity in years.