A Kyrgyz-born Russian citizen was identified Tuesday as one of the suspects in the deadly St. Petersburg subway bombing that left 14 dead and dozens injured.

Akbarzhon Dzhalilov is believed to be between 21 and 22 years old, Kyrgyzstan’s State Committee for National Security said in a statement. Authorities did not know his specific role in the bombing.

Russia nor in Kyrgyzstan authorities have specified whether the attack was a suicide bombing or whether the bomber got away. The Interfax news agency said authorities believe the suspect was linked to radical Islamic groups and carried the explosive device onto the train in a backpack.

There were two bombs planted at the subway, only one exploded. Both bombs were filled with shrapnel, Sky News reported. The unexploded device was rigged with up to 2.2 pounds of explosives, Russian media reported.

The entire St. Petersburg subway system was shut down and evacuated, but partial service resumed after about six hours.

Russian President Vladimir Putin said investigators were looking into all possible causes. President Trump called it "absolutely a terrible thing," adding, "it’s happening all over the world." Putin was visiting the city at the time, the second-biggest in Russia and his hometown.

Late Monday, the White House said Trump called Putin to express his condolences for the bombing and to offer the full support of the United States "in responding to the attack and bringing those responsible to justice."

St. Petersburg, like Moscow, is home to a large diaspora of Central Asian migrants who flee poverty and unemployment in their home countries for jobs in Russia. While most Central Asian migrants in Russia have work permits or work illegally, thousands of them have received Russian citizenship in the past decades.

Russian authorities have rejected calls to impose visas on Central Asian nationals, hinting that having millions of jobless men across the border from Russia would be a bigger security threat.

The Associated Press contributed to this report.