It was a run-of-the-mill complaint — a smell of gas — with a troubling explanation: Someone had improperly tapped into a Manhattan building's gas line, and it was leaking.

The issue was quickly resolved. But seven months later, authorities suspect another round of gas-pipe tampering caused a fiery explosion at the same building, killing two people, injuring nearly two dozen and leveling three buildings in all.

While officials caution that they aren't certain of the cause of last week's blast in New York's East Village, it is highlighting a long-known problem with potentially deadly consequences: untrained schemers rigging up pipes to save money by siphoning natural gas.

While statistics on its prevalence are limited, the president of New York's Consolidated Edison, the utility that serves the building involved in the blast, called it "fairly uncommon." Mayor Bill de Blasio said New York officials so far aren't hearing of any gas-tapping trend, "but we're going to look at everything once we have the full conclusions."

Some who have worked in the industry, however, say it's an all-too-familiar bane around the country.

"It's a regular, regular problem," said industry expert Mark McDonald of Boston-based NatGas Consulting. "Just as you can imagine theft in a Wal-Mart, no different — but it's much more dangerous."

Federal databases show 11 gas pipeline mishaps nationwide attributed to intentional damage, which could include stealing as well as sabotage, since 2010. But the data generally include only major incidents and exclude episodes involving small gas pipes that run within buildings or between buildings and their gas meters — lines that generally are the responsibility of property owners, not gas utilities.

Gas companies commonly build theft losses into rate calculations, but they're lumped in a category with leaks and other "lost and unaccounted for" gas.

Unauthorized gas hookups have been blamed or suspected in explosions, fires and deaths, including a 2010 Detroit house fire that killed three children, a 2008 Detroit home explosion that sent five people to hospitals and a 2007 blast in a central California garage. In 1991, three people were killed and 31 injured in two Brooklyn apartment buildings after a thunderous blast from a buildup of natural gas likely caused by an illegally tapped gas line.

McDonald estimates he or colleagues found an unsanctioned hookup about once a week during his 25 years as a Boston-area gas worker. Some crude set-ups used simple garden hoses to siphon the gas, while other, more elaborate schemes involved underground lines dug into a gas main.

"I've seen everything from complete morons to really detailed theft," he said.

Regardless how sophisticated, experts say it's risky for amateurs to rig up gas pipes. A simple spark can turn a gas leak from a poorly attached line into an explosion if the gas concentration hits 5 to 15 percent of the air in a given space, according to the American Gas Association.

Utilities can catch bootleg hookups by tracing leaks to their source, conducting routine inspections, and monitoring bills that drop abruptly. But siphoning can be a challenge to detect.

Some setups tap a gas company line before it hits a meter. Others — particularly in apartment houses and other urban settings — pilfer from neighbors' pipes. The victims may notice their bills rising and alert their gas companies, but such complaints can be tough to tease out among the many laments that companies get about the cost of gas.

Utilities more often pursue civil means than criminal prosecutions to recover their losses from gas theft. But there have been some criminal cases. An Allentown, Pennsylvania, landlord was charged in 2011 with "risking a catastrophe" for allegedly redirecting natural gas to heat two of his properties.

The Manhattan district attorney's office is involved in the investigation into last week's blast in New York; the office has declined to comment on it.

De Blasio said Monday he has not ruled out policy changes, or tougher penalties for those caught tampering with gas, but the investigation must conclude first.

The landlord at the East Village building where the blast happened, amid renovations, hasn't immediately responded to repeated calls and emails since the explosion. A possible phone number for a plumbing contractor who apparently was working on the building is temporarily disconnected. A lawyer for general contractor Dilber Kukic, declined to comment on the investigation.

"People should not speculate as to what happened, what caused it to happen, until evidence is released," attorney Mark Bederow said.

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Associated Press writer Jonathan Lemire contributed to this report.