A Nationwide Search Is On in Moscow Blast

A nationwide manhunt for those behind a deadly bomb blast here was in full swing Thursday, as officials announced that one of the injured had died, bringing the death toll to eight.

The Emergency Situations Ministry said others were still in critical condition. More than 90 people were injured in the Tuesday evening blast.

Nerves were on edge in the Russian capital, where many people are still fearful after a wave of apartment building bombings that killed about 300 people in Moscow and two other cities in September.

Frightened residents of several buildings ran out into the street Wednesday night, fearing that a bomb had gone off after someone tossed a firecracker in one neighborhood, the Itar-Tass news agency reported. Scores of people called authorities about suspicious boxes and bags that turned out to be filled with garbage, it said.

About 200 people sought help from an emergency psychological clinic set up after Tuesday’s blast, Tatyana Dmitrievna, director of the Center for Social and Forensic Medicine, told the NTV television station.

Newspapers ran four computer sketches of men whom police suspect in the blast, which tore through an underpass at the height of the evening rush hour.

Russian officials blamed the attack on Chechen separatists, but investigators and President Vladimir V. Putin have said they are not yet sure whether the strike was linked to the 10-month-old Chechen war or was a gangland-style crime.

Russian criminals often use explosives to settle scores, although such attacks rarely harm passersby.

Chechnya’s pro-independence president, Aslan Maskhadov, has denied any responsibility.

The FSB security police contributed to early suspicions of a link to Chechnya on Wednesday by announcing that two men, one a Chechen and one a native of a neighboring region, had been detained.

“We do not exclude they were both behind the terrorist act,” Vladimir Pronichev, first deputy head of the FSB, said in disclosing the arrests.

But prosecutors made clear Thursday that they had not linked the men, or any other suspects, to the attack.

Police have heightened security throughout the Russian capital, performing spot checks of documents of those with dark complexions.

Chechens and other people from the Caucasus say they fear a campaign of racial harassment, and liberals warned against an ethnic witch hunt.