BEDFORD - The cause of a three-alarm fire that destroyed part of an office building and tied up traffic for hours on Tuesday night remains under investigation.

According to Fire Chief Scott Wiggin, no one was injured in the blaze at the Daniel Webster Office Park on the Old Route 3, located south of Target and Lowe's and the new bridge that crosses the Everett Turnpike, but the call came in just in time for the evening commute.

"We received a call of fire through a roof at 288 South River Road at about 5 p.m.," Wiggin said, and when crews arrived, fire could be seen coming from both the roof and windows of the building.

"It was fairly well-involved at that time," Wiggin said.

Wiggin described the scene as a "nightmare" for police officers diverting traffic.

South River Road, Technology Drive and half of Hawthorne Drive were closed and motorists were directed to the Everett Turnpike and other alternate routes.

Wiggin said the fire started in an attic space, which was a lightweight truss type of construction.

"It's like a box of kindling," he said.

While one portion of the structure was a total loss, Wiggin said the building was in an "L" shaped configuration and a firewall separating the two buildings likely saved the second.

"We were able to control it at the firewall," he said. "That's the intention of firewalls, to give you that barrier, that line of demarcation."

Seven communities provided mutual aid, including Goffstown, Merrimack and Londonderry, with New Boston and Hooksett providing station coverage.

An excavator was brought in to turn over debris, allowing firefighters to check for hot spots, and South River Road re-opened at about 9 p.m.

kremillard@newstote.com