As NATO investigates the crash of a Chinook helicopter in Afghanistan on Friday--which killed 38 people, including 22 Navy SEALs, in the deadliest single incident in ten years of war--suspicions are surfacing that foreign assistance helped the Taliban pull off the sophisticated attack. An unnamed Afghan official tells AFP today that a Taliban commander and four Pakistanis laid an "elaborate trap" on Friday, luring "U.S. forces to the scene by tipping them off that a Taliban meeting was taking place" only to attack the helicopter with, in the official's words, "multiple shots" from "rockets and other modern weapons." NATO announced today that the Chinook was downed "by an insurgent rocket-propelled grenade" while coming to the assistance of ground troops engaged in a firefight with insurgents in Wardak province.

Ever since the incident, however, some analysts and politicians have speculated about whether the Taliban is solely to blame for the assault. On Sunday, Politico's Mike Allen posted an email from an unidentified sender raising the possibility that Iranian intelligence had a hand in "training and equipping" the Taliban to carry out the operation. Today, another unidentified source tells Allen that he suspects Pakistan, not Iran. "Ninety-nine percent of fighters and weapons [in Wardak province] likely all came from Pakistan," the source notes. In an interview with Bloomberg over the weekend, British MP Mark Pritchard claimed Iran has been training Taliban fighters in the use of surface-to-air missiles and may now be supplying the militant group with advanced weapons as well.

This isn't the first time that Pakistan or Iran has been accused of assisting the Taliban. Last year, The Guardianciting WikiLeaks cables, noted that intelligence reports warned of Iranian or Pakistani support around the time that the Taliban shot down another Chinook helicopter over Helmand province in 2007 with a shoulder-launched surface-to-air missile, or Manpad. "One unidentified source told an American officer that seven Manpads purchased by Iran from Algeria had been 'clandestinely transported from Mashhad in Iran across the border into Afghanistan,'" the paper explained. "Other reports, also unconfirmed, accused Pakistan's Inter-Services Intelligence of supplying weapons or missile-trainers to the Taliban." Last month, Kandahar's police chief told Afghanistan's TOLO News that Pakistan and Iran were providing "safe havens" for Taliban leaders. Other reports last year suggested that Taliban fighters were training in Iran and using Iranian weapons.

But others are skeptical of these assertions. While U.S. officials have occasionally hinted that Taliban militants are receiving weapons from Iran, former Defense Secretary Robert Gates has described Iranian support for the Taliban in Afghanistan as "pretty limited." And, as The Wall Street Journal noted last year, some analysts argue that while Shiite Iran may be an enemy of the U.S., it also doesn't want to see the Sunni Taliban destabilize Afghanistan. "The U.S. needs a stable Afghanistan so al Qaeda and other terrorist groups don't again form operating bases there," the paper explained. "Iran needs a stable border free of refugees and drug trafficking."

Whether or not Iran or Pakistan had anything to do with the Taliban's most recent attack, Wired notes that the militant group may have used a new weapon on Friday--"Improvised Rocket-Assisted Mortars," which first appeared in Iraq in 2008 and "combine traditional tube mortars with rocket boosters and, in many cases, remote triggers, allowing insurgents to fire them from a distance." But NATO spokesman Carsten Jacobsen has cast doubt on that claim, telling AFP that "we're not seeing any specific new types of weapons on the battlefield."

On Monday, another NATO helicopter made a "hard landing" in eastern Afghanistan, but a NATO official reported no casualties or enemy activity, according to AFP. The Taliban, which is prone to exaggeration, told Reuters that the group had also shot down this aircraft, another Chinook, and killed 33 American soldiers.