It was the second such forced landing this month. The plane was released after the check.
The move appeared aimed at easing U.S. concerns that Iraq has become a route for shipments of Iranian military supplies that might could Syrian President Bashar Assad battle rebels in his country's civil war.
The head of the Iraqi Civil Aviation Authority, Nassir Bandar, said the inspection took place Saturday. The inspectors allowed the plane to continue its flight after they determined there were no weapons onboard, he said.
"Our experts found that the plane was carrying only medical supplies and foodstuffs," Bandar said, "so the flight was allowed to proceed."
Bandar said Iraqi authorities would continue searching planes suspected of transporting arms to Syria. Iraqi officials have repeatedly said they would not allow their country or airspace to be a corridor for arms shipments to either Syrian government forces or rebels.
Iraq ordered another Iranian cargo plane to land for inspection on Oct. 2. No weapons were found in that search, either.
Last month, Iraq banned a North Korea plane from crossing its airspace because of suspicions it was carrying weapons to Syria.
American officials have expressed concern that Iranian planes may be ferrying weapons over Iraq, and they have pressed Baghdad to take stronger action to ensure that no such transfers occur.
Also Sunday, police said three people were killed and eight others wounded when two bombs exploded near a market southeast of Baghdad.
Police said the simultaneous attacks Sunday morning took place in Madain, about 20 kilometers (14 miles) southeast of Baghdad, as shoppers started to arrive.
Medics in a nearby hospital confirmed the casualties. All officials spoke on condition of anonymity because they were not authorized to talk to reporters.
Sunday's blasts followed a string of attacks that killed 40 people in the Iraqi capital a day earlier, including evening explosions near a market and a bus station in the Shiite neighborhood of Sadr City.
Saturday was the deadliest day from attacks in nearly six weeks.
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