By Joe Shortsleeve, WBZ-TV

BOSTON (CBS) – Tonight, there are serious questions about a deadly crash. Investigators are now trying to figure out why a potentially dangerous dump truck — that may have been recalled — was on a busy highway.

Chief Correspondent Joe Shortsleeve says the matter has been referred to the district attorney’s office for possible criminal charges.

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It happened Friday afternoon on busy I-495. A backhoe being towed by a National Grid truck flipped off a trailer and landed on a mini van killing an elderly Westford woman and seriously injuring another woman.

WBZ-TV’s Joe Shortsleeve reports

Sources tell WBZ it was not a union member but a rather a manager from National Grid who was behind the wheel at the time of the crash. National Grid said it was conducting a truck safety test after union members raised concerns. Robert Mahoney, a national representative for the Utility Workers of America, tells WBZ, National Grid told some Union members two weeks ago not to drive those particular trucks.

Monday morning in a memo to employees obtained by WBZ, National Grid banned further use of similar trucks saying “…as a precaution, we have removed from operation dump trucks of the same model/year as the one involved in the accident pending the results of our investigation.”

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Witnesses on Friday told WBZ the six wheel truck began fish tailing across the highway ejecting the backhoe.

WBZ has confirmed this truck may be part of a safety recall by the federal government. A memo from the trucks manufacturer to the federal government in July 2009 says:

“A failed steering shaft could cause a loss of vehicle control and a crash may occur.”

It is unclear tonight whether the National Grid truck was actually one of those recalled. However the state police said today…“we will look at all potential contributing factors… and the decision to conduct a safety test on the truck at that time and place.”

Relatives of the Westford woman who died in the crash have not issued any kind of statement choosing not to talk to reporters today.

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A spokesperson for National Grid refused comment today while the investigation is on going. WBZ has been told by multiple sources that this particular truck was equipped with a video camera suggesting there is a very strong possibility that the crash itself is on tape, as well as audio of the National Grid manager who was behind the wheel. And union members are also saying that it is very unusual for a manager to actually be driving one of these six wheel trucks.