Boston, MA – CBS4 – It was July 2002 when young Iris and Violet Carey were killed in a gas explosion in their Hopkinton home, a sobering reminder of the destructive power of a natural gas leak.

“When you’re in your house and you go to sleep at night, and you have natural gas, you want to feel safe,” says Tara Carey, the girls’ mother.

And you expect your gas company to be doing everything possible to guarantee that you are safe.

A month long I-Team investigation has found that two of the three major gas companies in this state are ignoring important federal regulations designed to protect you, and that the state’s public utility commissioners are letting them get away with it.

Federal regulations require gas companies to inspect the gas piping that comes into your home and connects with your gas meter every three years for corrosion, and every five years for leaks.

Mark MacDonald is president of the Union of Gas Workers who would do those inspections. “These inspections are not being conducted,” he told our I-Team.

Both Keyspan and N-Star Gas admit they are not inspecting the gas lines inside homes as required by federal regulations. Instead, they say, they inspect when they change gas meters (every 7- 10 years) or when responding to emergency calls.

We were shown a corroded gas pipe in a Gloucester home that had gone un-inspected for 10 years. “It’s beyond a point where it should be addressed,” MacDonald said.

Nicole Alves, who lives there, just gave birth. “They’re not doing their job. It gets me nervous,” she said.

Should homeowners using natural gas be concerned?

Charles Batten is the former Chief of Pipeline Accident Investigations for the National Transportation Safety Board. “I think there is substantial risk,” he told us. “It’s not unusual to have piping inside the house leak and cause an explosion or fire.”

That’s what happened in Hopkinton, in the explosion that killed 4 year-old Iris and 5 year-old Violet. When the state investigated the explosion, documents show the state cited N-Star Gas for failing to inspect the indoor gas piping as required by federal regulations.

But, believe it or not, almost four years after this deadly accident, the state’s Department of Telecommunications and Energy, our public utility commission, is still not making sure gas companies are obeying the law.

“I have grave concerns about that,” said State Senator Jack Hart of Boston. “The gas companies are approaching this in Massachusetts as if they have carte blanche.”

Another problem, to prevent house explosions federal regulations require gas companies to make sure there is a gas shut off valve, or gate box, outside your home that is easily accessible.

At the scene of a gas explosion at a Weston home last fall, fire captain Peter Walsh told us, “the gas shutoff was not able to be found quickly.”

The I-Team visited a home in Lynnfield. “As you can see there is no gate visible form here to the home,” MacDonald of the Union of Gas Workers pointed out.

“Thousands of shutoffs are paved over,” says Ed Kelly of the Boston Firefighters Union. “If it doesn’t get addressed, people are going to die.”

Executives from N-Star Gas and Keyspan refused to go on camera.

So we contacted Northeast Gas Association spokesman Tom Kiley, who contradicted what the gas companies told us off camera. “The local gas companies do have very comprehensive programs to meet these statutes.”

“But it’s not happening,” the I-Teams Joe Bergantino said to Kiley.

”We are working with the Department of Telecommunications and Energy on interpreting these standards,” Kiley responded.

Bottom line, our investigation found Keyspan and N-Star Gas are not inspecting the gas lines to your meter inside your home on a three to five year schedule.

As for shut off valves, the gas companies say they try to make them accessible when streets are repaved.But fire officials and federal regulators say that’s not good enough.

If you’re concerned about this, and experts say you should be, call your gas company and set up a time to inspect your home.

In a written statement Keyspan issued in response to our investigation, the company says it’s working with the American Gas Association and federal regulators to address the issue of indoor gas piping inspections.Baystate Gas says it’s now doing those inspections on a regular basis.

As for the Department of Telecommunications and Energy, it has just announced it will investigate whether gas companies are obeying federal rules requiring accessible shut off valves. State Senator Jack Hart told the I-Team he will call for hearings on Beacon Hill if the commissioners continue to ignore federal law.