MOSCOW (AP) — A blast in an upscale residential block in Moscow killed one person and wounded four others on Monday morning, Russian news agencies reported, citing emergency officials.

Those wounded in the blast, the cause of which was not revealed, were hospitalized in grave condition, Russia's state news agency RIA Novosti reported, citing Moscow health officials.

The authorities said a criminal case has been launched into the explosion, but they didn't say on what charges. Footage released by Russia's main investigative agency, the Investigative Committee, showed a building hall with glass doors shattered and suspended ceilings torn up.