The aircraft, which was flying to China from the United Arab Emirates, landed in the eastern Indian city of Calcutta for refueling Sunday, said Jayati Ghosh, a senior airport security official.

Indian customs officials found arms and ammunition during a customary check of the aircraft, said Wing Cmdr. Mahesh Upasani, an Indian air force spokesman.

The 10-member crew were being questioned about why they failed to declare the plane's cargo, he said.

On the customs form, "the operator had written that they are not carrying arms and ammunition," Upasani told the CNN-IBN television channel.

He said he did not know the type of weapons and the quantity on board as the matter was being investigated by customs authorities.

"We are finding out whether this lapse was because of a communication gap or otherwise," Upasani said.

Ghosh said the aircraft had not been cleared to leave India by Monday afternoon.