A Mexican judge has dropped the criminal charges involving a 2010 blast at a Playa del Carmen resort that killed seven people, including five Canadians, CBC News has learned after obtaining an email from Foreign Affairs.

The blast ripped through part of the Grand Riviera Princess Hotel in Playa del Carmen last November, injuring 17 people and killing seven.

Terra Charmont, an Alberta woman who lost her husband and son in the explosion, said it was a blow to hear that the charges have been dismissed.

Christopher Charmont and his son John were among the Canadians killed in the hotel blast. (Toronto Star)

"There hasn't been any justice served… it was just very disappointing," she said.

There were several theories about what caused the blast, but it was ultimately revealed that there was an unauthorized extension of a gas line under the hotel's lounge. The line had apparently been damaged and leaked prior to the explosion, said Mexican Attorney General Francisco Alor.

Five people, including contractors and workers at the resort, faced charges ranging from homicide to professional misconduct after the blast.

An email from Canada's Department of Foreign Affairs said the "judge indicated that after reviewing the elements brought forward, these did not prove that the defendants had committed a crime."

CBC's Alicia Asquith said the judge didn't find enough evidence proving exactly who was to blame and concluded the case would be better suited to civil court.

That decision was "baffling," according to Russ Brown, an Edmonton lawyer helping families associated with the case.

"When you have an event of this magnitude, with an explosion, tampered building plans, with multiple fatalities, you would think there would be some sort of consequences visited," he said.

He said the lack of conclusions in the case should have led to a larger inquiry, not to charges being dismissed.

Charmont is pursuing a civil suit. She said she would also like to see the Canadian government "supporting its citizens a lot more, and we haven't received any support from that end either."

With files from CBC's Briar Stewart and Alicia Asquith