China appears to be building hundreds of new silos to house intercontinental ballistic missiles, raising some questions about its intentions. To some experts Insider talked to, the huge silo fields look to be China’s answer to rivals that have a lot more nuclear weapons.

In recent months, analysts with the Federation of American Scientists and the Middlebury Institute of International Studies (MIIS)  relying on commercial satellite images have found that China is constructing what looks like around 250 new missile silos. It previously had only about 20 silos.

Silo construction is clearly visible and appears to be underway in Hami in Xinjiang province, Yumen in Gansu province, and Jinlantai in Inner Mongolia. The Hami site, which is still in the early stages of construction, is roughly 300 square miles and the Yumen site is around 700 square miles.

The silos are grouped but spaced roughly two miles apart in grid patterns, which is very different from the way China has approached silos in the past. The country’s older silos are scattered, isolated, and somewhat camouflaged.