(CNN) -- The Yemen-based arm of the al Qaeda terrorist network claimed responsibility Friday for last week's plot to send explosive devices on cargo planes bound for the United States.
Al Qaeda in the Arabian Peninsula, which had been suspected in the plot, posted its claim on various radical Islamist websites, saying, "We will continue to strike blows against American interests and the interest of America's allies."
The statement also claimed the group is responsible for the crash of a UPS cargo plane in Dubai, United Arab Emirates, on September 3.
Investigators said earlier this month they had failed to turn up any evidence that terrorism was involved in that crash, which killed the two pilots aboard, according to a U.S. government official.
About 45 minutes after UPS Flight 6 departed Dubai International Airport for Cologne, Germany, the crew declared an emergency due to smoke in the cockpit. They asked to return to Dubai, but shortly before the plane could get to the airport it crashed.
Officials in the United Arab Emirates have said -- and a U.S. official confirmed -- that the plane's cockpit voice recorder has been examined and nothing on it indicates an explosion. Explosions have distinctive sound signatures, and that would have been recorded on the device, the official said.
The UAE said it has "eliminated the possibility of an onboard explosion, following a detailed onsite investigation of the wreckage."
A U.S. counterterrorism official said Friday that while "there are very strong indications that AQAP was responsible for plotting last week's disrupted cargo plane plot ... we can't confirm at this point their claims about the early September incident."
White House counterterrorism chief John Brennan said Sunday that the United States is "looking very carefully" at the September crash to see if it could be related to the recent terror threat involving cargo aircraft.
The latest threat was revealed October 29 when authorities in the United Arab Emirates and Britain found two explosives-laden packages sent from Yemen that were addressed to synagogues in Chicago, Illinois.
The statement by al Qaeda in the Arabian Peninsula said that since Western media did not link the September UPS plane crash to the group, "we decided not to announce it so we could carry on a similar operation."
"We did that this time using two devices, one of which was sent via the American UPS company and the other via the American FedEx company," the statement said.
The devices, loaded with the powerful explosive PETN, were packed in computer printer toner cartridges and designed to be detonated by a cell phone, a source close to the investigation has said.
Friday's claim of responsibility by al Qaeda in the Arabian Peninsula warned that "since both operations were successful, we intend to spread the idea to our mujahedeen brothers in the world and enlarge the circle of its application to include civilian aircraft in the West as well as cargo aircraft."
U.S. investigators believe that al Qaeda bombmaker Ibrahim Hasan al-Asiri, 28, is linked to the packages, according to a federal official who was briefed by authorities. Al-Asiri, who is thought to be in Yemen, is a Saudi who ranked high on Saudi Arabia's list of most wanted published in February 2009. He is also believed to be the bomber who designed last year's failed attempt to blow up a U.S. airliner as it landed in Detroit, Michigan, on December 25.
A U.S. official said that the devices found in the packages last week were very sophisticated and could have exploded in flight, but it wasn't clear whether that was the intent.
The group's statement said the devices' designs "allow us the opportunity to detonate them in the air or after their arrival to their ultimate destination, and they are designed to pass through all detectors."
The packages were discovered thanks to a tip from Saudi Arabia. Saudi officials provided tracking numbers of the two packages bound for Jewish organizations in the United States, enabling quick tracing to the United Kingdom and Dubai, a source told CNN.
Friday's statement denounced the Saudi assistance in thwarting the plot, saying, "God has exposed you and showed the world that you are nothing but treacherous agents to the Jews because these bomb packages were headed to Jewish-Zionist temples, and you had to intervene with your treacherous ways to protect them, so may God curse you for being the oppressors."
But two U.S. officials said that the street addresses found on the packages were not the current locations of the synagogues and that the packages were addressed to historical figures from the Crusades and the Spanish Inquisition.
After last week's incidents, U.S. government authorities grounded packages originating from Yemen destined for the United States.
Yemen has asked for outside help to thwart terror groups, but the country, the ancestral home of Osama bin Laden, is still used for operations, U.S. officials say.
CNN's Saad Abedine contributed to this report.