(CNN) -- Two people suspected of involvement in the deadly bombing at a Minsk subway station were detained late Tuesday night, Belarus Deputy Prosecutor General Andrei Shved said at a news briefing Wednesday.
"These are two people with whom investigative procedures are being conducted, who have undergone first interrogations in the presence of lawyers, and first testimony has been obtained from them," Shved said.
Both men are citizens of Belarus and have known each other for a long time, Shved said.
Based on a closed-circuit TV camera recording in the Minsk subway, "there are very solid grounds to presume that one of the detainees was the perpetrator," he said. Twelve people were killed in the attack, authorities said.
Shved said the recording clearly reveals that one of the two suspects arrived at the Oktyabrskaya subway station, left a bag at a bench and retreated. Soon after the bomb went off.
Shved didn't give the suspect's name, only saying that he was born in 1986. No details were reported about the second man.
Before the arrests, authorities released a description of a suspect, who they said was a 27-year-old man.
"We now know the main thing -- who committed this terror act and how. So far we don't know why they did it -- but we'll find that out soon, and this is our main task today," Belarusian President Alexander Lukashenko said Wednesday.
Lukashenko said the detained suspects have also confessed to committing terrorist attacks on Independence Day in Minsk on July 3, 2008 and in city of Vitebsk in September, 2005. Nobody died in those bomb attacks but several dozen people were injured in each of the bombings.
Also, the president ordered law enforcement to question some opposition figures over the bombing.
"We are looking for accomplices and perpetrators of the metro bombing. Perhaps these people (opposition figures) ... will open their cards and tell us who ordered (the bombing)," Lukashenko said.
Preliminary findings suggest the blast was caused by a radio-controlled device and that no suicide bombers were involved, Belarusian officials said.
The Belarusian KGB is considering three possible motives behind the bombing, including an attempt at destabilizing the security situation in Belarus, revenge by extremist organizations, and an act by a madman, officials said.
A train was standing at the Oktyabrskaya metro station when the handmade bomb planted under a bench exploded Monday, officials said.
The bomb, with estimated power equivalent of 5 kilograms of TNT, was stuffed with shrapnel, nails and small metal balls, the state-run news agency Belta reported, citing security officials.
The death toll rose to 12 when one of the victims died in a hospital early Tuesday, the RIA Novosti news agency reported.
Victims' families will receive $10,000 from the government and their funeral expenses will be covered, Belarus state media reported Tuesday. Funerals are expected to take place Wednesday and Thursday, according to the city hall in Minsk.
CNN's Maxim Tkachenko contributed to this report