Explosion at steel plant leaves one dead and dozens hurt

The Clairton Coke Works was rocked by a major explosion (Gene J Puskar/AP)

An explosion at a US Steel plant near Pittsburgh left one dead and dozens injured or trapped under the rubble on Monday, with emergency workers on site trying to rescue victims, officials said.

The explosion sent black smoke spiralling into the midday sky in the Monongahela Valley, a region of the state synonymous with steel for more than a century.