Tasnim � Explosion in a road tunnel under construction in northern Iran killed at least three workers.

The explosion occurred on Tuesday morning at a tunnel in an under-construction highway connecting Iran�s capital of Tehran to the northern province of Mazandaran.

The blast and consequent fire blocked the tunnel entrance, leaving several workers stuck inside.

Spokesman for the Emergency Medical Service of Mazandaran said three workers have died and 8 others have been injured in the accident.

A number of victims retrieved from the road tunnel have been taken to the hospital with severe burns.

The construction of the road, known as Tehran-North freeway, has been in progress for three decades.