Al-Qaida considered attacking U.S. trains on the 10th anniversary of the 9/11 attacks, according to an initial look at DVDs, computers and other documents seized at the raid on Osama bin Laden's home, NBC News reported.

However, U.S. officials told NBC News that they have no recent intelligence indicating such a plot is active.

The information about a possible train plot is the first intelligence revealed from the trove of material found in the attack on bin Laden's compound. Officials said they found what they call "aspirational" items — things al-Qaida operatives were interested in trying to make happen.

A government advisory obtained by NBC News and sent to the rail industry said that as far back as February 2010, al-Qaida was contemplating "an operation against trains at an unspecified location in the United States on the 10th anniversary" of the 9/11 attacks.

One option, the advisory said, was trying to tip a train by tampering with the rails so that the train would fall off the track at either a valley or on a bridge. Such an attempt would probably only work once, the material in bin Laden's house said, because tilting or tampering with the rails would be spotted, the advisory said.

Other material mentions a desire to target big mass-transit hubs, an interest long understood because of the history of al-Qaida attacks on rail targets in Spain, the United Kingdom and India.

The FBI and Homeland Security are encouraging local governments to maintain vigilance. But there are no plans to issue a terrorism alert, because there is still no specific or credible intelligence of any actual attack plan in the works, NBC News said.

Homeland Security spokesman Matt Chandler issued a statement Thursday that the department has no information on "any imminent terrorist threat to the U.S. rail sector, but wanted to make our partners aware of the alleged plotting; it is unclear if any further planning has been conducted since February of last year."

"We want to stress that this alleged al-Qaida plotting is based on initial reporting, which is often misleading or inaccurate and subject to change," Chandler said.

He said the department and its partners since Sunday have reviewed protective measures for all potential terrorist targets, including critical infrastructure and transportation systems across the country and deployed additional officers to non-secured areas at airports.

They also are identifying "any new targeting rules that should be instituted to strengthen the ways we assess the risk of both passengers and cargo coming to the United States," Chandler said.

It’s taking time to analyze all the material found in the house because some of it is encoded, according to officials briefed on the contents, and little, if any, of it is in English. A call has gone out throughout the federal government for Arabic speakers who have the highest level of security clearance to help with translating the material.

The assault team took five cell phones, five computers, 10 hard drives and more than 100 storage devices from the compound, along with other objects, such as guns, papers and clothing. Two senior U.S. officials told NBC News that people in the compound were using cell phones to communicate, a gaping hole in security around bin Laden.

A senior official said that the material taken from bin Laden's house in Pakistan was first taken to a U.S. base in Afghanistan, where it was quickly skimmed for any urgent information. It was then turned over to the FBI, so that a legal chain of custody could be established in case any of the material is needed to prosecute terrorists.

The FBI flew everything to its facility in Quantico, Va., where technicians immediately began making copies of all the computer files for distribution to various intelligence agencies — the CIA, NSA, DIA, "anyone who would have some perspective on what was found."

Individual files found in the house are being examined by several agencies at the same time.

The FBI is maintaining custody of physical objects to study the items for fingerprints, DNA material or and anything else that could be of value, officials told NBC News.