Updated at 11:20 a.m. ET
An explosion ripped through a train car in the metro system in St. Petersburg, Russia, Monday afternoon. The official death toll has fluctuated, with different officials saying that either nine or 10 people were killed. Dozens have been reported wounded.
The city's governor, Georgy Poltavchenko, told the state-run TASS news agency that 10 people had died; in a separate statement, the National Anti-Terrorist Committee said there were nine dead and 20 wounded, according to local media. The reason for the discrepancy wasn't immediately clear.
Poltavchenko's office said 43 injured people were taken to hospitals after the blast in Russia's second-largest city.
"The blast happened between two stations, but the driver made a right decision not to stop the train and took it to the next station so that passengers could evacuate and the injured could be helped," said spokesperson Svetlana Petrenko of the Investigative Committee of the Russian Federation, which is now in charge of the investigation.
"It is possible that this helped avoiding even more victims," Petrenko said, praising the train driver.
TASS posted a YouTube video with cellphone footage showing people walking through a smoke-filled station.
Initial reports had suggested two explosions had struck at the core of St. Petersburg — one in the Sennaya station and another at the Institute of Technology station that's one stop further south. But the RBC media outlet reports that the train was moving between those stations when the explosion hit. Citing Interfax, RBC says most of the damage was limited to one train car.
Reporter Charles Maynes told Morning Edition that police found an additional device at a different metro station, which failed to detonate.
"The causes [of the blast] are unclear, that's why it is early to speak about this now," Russian President Vladimir Putin said Monday, according to TASS, which quoted him as saying that "investigators are considering various theories, including those linked to terrorism."
Putin was in St. Petersburg attending a pro-Kremlin media forum, Maynes added. In a post on Twitter, he vowed to take "all necessary measures to provide assistance to those affected" by the blast.
Video posted on social media showed rescue workers rushing to the scene. An image posted by another Russian state news agency, RIA, shows a damaged metro car and scattered debris.
The station was evacuated and seven other stations were closed in the city, TASS added. Police are in the process of questioning witnesses and metro employees, according to RIA.
The explosion happened in central St. Petersburg, which is popular with tourists, Maynes reported. He said that while authorities have not suggested who, if anyone is responsible, there are several "likely suspects":
"One is, of course, ongoing problems they have with the Northern Caucasus. They've had several wars in Chechnya, the breakaway republic, which has essentially gone much quieter in recent years but I think there's a suggestion that that's a possibility.
"More likely, though, is ISIS, frankly. Russia of course went into Syria, where they've been combatting ISIS in theory though many say they're also supporting the Syrian leader Bashar al-Assad."
The U.S. Consulate in St. Petersburg issued an emergency message to American citizens in the city, telling them to avoid the area.
"Review your personal security plans; remain aware of your surroundings, including local events; and monitor local news stations for updates," the consulate statement read. "Maintain a high level of vigilance and take appropriate steps to enhance your personal security."
This is a developing story. Some things that get reported by the media will later turn out to be wrong. We will focus on reports from police officials and other authorities, credible news outlets and reporters who are at the scene. We will update as the situation develops.