During this time the introduction of steam-powered transportation and printing technology was facilitated by European expansion. As a result, the interaction between Indonesia and the rest of the Islamic world, particularly the Middle East, had significantly increased. In Mecca, the number of pilgrims grew exponentially to the point that Indonesians were markedly referred as "rice of the Hejaz." The exchange of scholars and students was also increased. Around two hundred Southeast Asian students, mostly Indonesian, were studying in Cairo during the mid-1920s, and around two thousand citizens of Saudi Arabia were Indonesian origin. Those who returned from the Middle East had become the backbone of religious training in pesantrens.