Contrary to counterterrorism expert Richard Clarke’s recent assertions, liquefied natural gas tankers in Boston Harbor were never used to transport terrorists, Boston FBI spokeswoman Gail Marcinkiewicz said in a telephone interview this week.

Clarke, a former White House counterterrorism czar, says in his book, Against All Enemies, that al-Qaida operatives boarded LNG tankers in Algeria and used them to gain entry into Boston Harbor. Clarke also wrote that the tankers in Boston Harbor were top target concerns for federal officials on Sept. 11, 2001 directly following the attacks on the World Trade Center and the Pentagon.

Simon ‘ Schuster/The Free Press, the publisher of the book, could not be reached for comment.

“We investigated the LNG tankers thoroughly … and concluded terrorists were not using the tankers,” Marcinkiewicz said. The investigation was carried out by a “multi-agency task force” that included the Boston Police Department.

BPD spokesman John Boyle would not confirm or deny the department’s participation in the investigation nor answer any questions of an “investigative” nature, he said in a phone interview Wednesday.

City officials, including Mayor Thomas Menino, were not notified of the investigation, though. According to Marcinkiewicz, there was “nothing to notify them about.”

“We follow up leads all the time,” she said. “We don’t call them and say, ‘This is what we’re working on today.'”

Marcinkiewicz declined to comment on Clarke’s assertion that the Boston Harbor tankers were a target for terrorism on and following Sept. 11, saying instead that “there are many, many targets in this city.”

According to www.naturalgas.org, LNG – created by cooling natural gas to about -260 degrees – is being used increasingly for the transportation of natural gas, because it takes up about one six-hundredth the volume of gaseous natural gas.

According to the website, “LNG, or any vapor associated with LNG, will not explode in an unconfined environment. Thus, in the unlikely event of an LNG spill, the natural gas has little chance of igniting an explosion.” Additionally, “it is typically transported by specialized tanker with insulated walls, and is kept in liquid form by auto-refrigeration.”

In a speech at the LNG Ministerial Summit in Washington, D.C. December, Energy Secretary Spencer Abraham said, “a record of 33,000 carrier voyages covering 60 million miles over a 40-year period without a major accident is compelling evidence of [LNG]’s safety.”

Historically, the most disastrous incident involving LNG occurred in 1944, when a LNG facility in Cleveland, Ohio experienced a tank failure resulting in a fire that killed 128 people. The cause of the fire, according to the website of CH-IV International (www.ch-iv.com) – a major energy service provider – was a newly installed tank built with low-nickel content. The inner tank was made of 3.5 percent nickel steel, a material now known to be susceptible to fracturing at LNG storage temperatures.