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. Last Updated: 07/27/2016

'Terrorist' Blast Kills 50 in Dagestan

Russian investigators said Monday that they believed a terrorist bomb caused a huge explosion over the weekend that collapsed a military housing block in southern Russia, crushing to death at least 50 people.

The Federal Security Service also reported that it had arrested one man suspected of involvement in the explosion, which destroyed a nine-story apartment block in the border town of Kaspiisk, near Russia's southern border with Azerbaijan.

With the death toll climbing as new bodies were being pulled from the rubble, President Boris Yeltsin declared Tuesday a national day of mourning to mark the tragedy.

Rescue teams were still searching Monday night for possible survivors buried under the debris of the Soviet-era concrete building, half of which folded Saturday like a pack of cards after the explosion. Thus far, 39 people have apparently been rescued from the ruins.

Russian television showed rescuers picking slowly through the rubble in the hope that there was still a chance of finding more people alive. At least 16 children were killed in the blast.

Russian Interior Ministry investigators told Interfax on Monday that the tragedy did not occur by accident.

"The explosive device was made and planted by one or several professionals, because the nine-story building collapsed without damaging the neighboring buildings," field engineers said.

"About a week before the explosion, a team of builders had worked in the building. The possibility of their involvement Kovalyov, whom Chernomyrdin has ordered to investigate the explosion, gave no further details.

Itar-Tass quoted official sources as saying the blast might have been a gangland attack in retaliation for a regional crackdown on arms and caviar smuggling. The building was occupied by Russian border guards and their families.

Border guards issued a statement describing the explosion as a "terrorist act" by cross-border criminals. "Those who thus intend to intimidate the border defenders are deeply mistaken," said the statement, which added that the losses had strengthened the guards' resolve to deal harshly with criminals.

The statement also called upon the relevant state institutions to deal with the "outrageous outburst of crime and terrorism" in the country.

Gangland violence has become commonplace in post-communist Russia. Earlier this month, 14 people died in a bomb blast at a Moscow cemetery in an apparent feud between factions of an Afghan war veterans' charity that has been linked to big business.

Kaspiisk also lies close to Chechnya, which caused some officials to speculate that there might be a link between the explosion and the rebel region where an uneasy peace is holding after a 21-month, bloody conflict between Russian forces and separatists.

But Chechen rebel leader Zelimkhan Yandarbiyev, whose aide worked out a new draft agreement with Moscow on Saturday, quickly denied that separatists were involved in the blast -- which he said was aimed at wrecking the peace process.