The families also reiterated their desire for a full public inquiry into the blast, along with the fatal accident inquiry that is already planned.
Their call was backed by Patricia Ferguson, Labour MSP for Glasgow Maryhill.
The lord advocate is currently considering whether a public inquiry will be held and a decision is expected within a month.
Elish Angiolini said she was in the process of deciding what type of inquiry would be most appropriate and would consult the families of those who died as well as looking at issues identified during the police and health and safety executive investigations.
A statement issued by both companies following the verdict said their thoughts remained "with those people most affected by the tragedy - the victims, their families, and all who were injured".
It added: "The information brought to light by the complex technical investigation and subsequent court proceedings will, we hope, have provided meaningful answers to many of the questions surrounding this terrible tragedy.
"Since May 2004, all concerned have made enormous efforts to sustain the companies and to maintain the employment of our workforce.
"The heroic input from so many who were injured in the blast, and the loyalty and support of many others, is the reason for the companies' survival to this day."
It went on to welcome "any form of inquiry that will properly establish all the facts and circumstances relating to the disaster".
Stewart Campbell, director of the Health and Safety Executive in Scotland, said it was important that lessons were learned from the case.
"I would like to remind all users and suppliers of LPG of the risk from buried pipes carrying LPG, particularly when located near areas where gas can accumulate", he said.
"Everyone should ensure that problems which are out of sight are not out of mind.
"The dangers posed by buried pipes can be overcome by a systematic approach to risk management and the findings of the investigation reinforce the need for effective arrangements for the maintenance, renewal or repositioning of buried pipes."
He added: "I would like to pay tribute to all my staff and those of HSL who have dedicated much of the last three years to the investigation and who responded magnificently to what has been an extremely testing investigation."
Grahame Smith, general secretary of the Scottish Trade Unions Congress (STUC), called for individual directors to be held liable for the health and safety failures of their companies.
He said: "No level of fine can adequately reflect the loss that these families have suffered. Our justice system appears to be totally inflexible in the sentences that judges can impose following breaches of health and safety legislation."
The record fine imposed on a firm for breaching health and safety legislation was £15m on utility firm Transco.
The company was convicted on a charge arising from an explosion which killed four people.
Andrew and Janette Findlay and their children Stacey, 13, and Daryl, 11, died in an explosion in Larkhall, South Lanarkshire, in December 1999.
The blast, caused by a leaking gas main, destroyed their home.