A group of students at Georgetown University started this as a homework project, but after analyzing China's huge network of tunnels for storing missiles for as long as three years under their professor, a former top Pentagon official, they made the conclusion that China's nuclear arsenal may be many times larger than previously estimated.

According to their report, China is hiding its ballistic missiles and nuclear warheads in a vast network of tunnels, which they called their Underground Great Wall.

Led by Phillip A. Karber, a professor, the university students have translated hundreds of documents, gone through satellite imagery, got Chinese military documents and searched through hundreds of gigabytes of online data, the Washington Post reported.

The students claimed in the report that China could have as many as 3,000 nuclear warheads, a significant increase from the previously estimated high of 400, Al Jazeera reported.

Currently, Russia, the U.S. and France possess the most warheads - 11,000, 8,500 and 300 respectively.

The students based their research not only on traditional documents, but also on Chinese state television, newspapers, blogs and even on Google Earth.

The 363-page study has not been published yet, but has been circulated at the Pentagon.

However, the U.S. experts, who track nuclear weapons and China's arsenal in particular, criticized the report's methods. A Pentagon official said there were no plans to alter the U.S. government's estimate of China's arsenal, the AFP reported.

China has not produced enough fissile material to produce 3,000 nuclear weapons, Hans Kristensen, director of the nuclear information project at the Federation of American Scientists, told AFP.

Nor do they have delivery systems for so many weapons. It's just inaccurate on all fronts that estimate.

Karber, who led the study, is speaking to Al Jazeera in the video below: