A construction worker in Alexandria was fatally injured yesterday when the unshored dirt walls of a newly dug trench at least nine feet deep collapsed and buried him, authorities said.

Mario P. Jurado, 56, of Falls Church was pronounced dead shortly after the arrival of Alexandria fire and rescue workers at the construction site at 3655 Wheeler Ave., according to fire department spokeswoman Jane Davidson.

"The site was not shored and the dirt fell in the trench as the men were preparing to install sewer lines," Davidson said. The accident occurred shortly after 9 a.m., she said.

A native of Bolivia, Jurado was employed by Independent Construction Co. of Fairfax, a subcontractor on a warehouse and office building project being developed by Bogle Development Inc. of Alexandria.

"I grabbed ahold of {Jurado} and tried to hold the wall of dirt back," said coworker Tom Elinsky, 24, of Alexandria, who was also in the trench when its walls collapsed. "Mario started running {to climb out of the hole} but it caved in on him."

The accident is under investigation by the city's code enforcement office, Assistant City Manager Thomas Brannan said. A safety enforcement inspector from Virginia's Department of Labor and Industry was also at the site yesterday, a department spokeswoman said.

"When you get over five feet in depth, you're supposed to have shoring to secure a hole," said Dan Cammer, a structural engineer for the Alexandria code enforcement office. "It's pretty obvious the ditch doesn't have any temporary shoring." He said he did not know if any code was violated in the accident.

Elinsky said he and another worker, Dan Campbell of Oxon Hill, immediately started digging to free Jurado. When rescue workers arrived, they had him dug out to his waist, Elinsky and Campbell said yesterday.