Tsering Shayka, a Tibetan historian, said ethnic conflicts had resurfaced in recent years with the gradual liberalization of China, in particular the relaxation of travel restrictions.
"What is happening now is that you have all this transient population. People are migrating here and there and coming into more and more day-to-day contact. In the past, they weren't allowed to trespass into each other's territory and you had no ethnic conflict," Shayka said.
Tibetans complain frequently about their culture being diluted when non-Tibetans, in particular Muslims, move into their areas and buy Tibetan businesses. That has been especially true in Lhasa, where Muslims now own many of the souvenir shops.
In the mid-1990s, Tibetans started boycotting Muslim restaurants in Lhasa after it was claimed that somebody had found a finger in a bowl of soup, setting off a rumor that Muslims were cannibals. Another rumor had it that Muslim cooks were urinating on food or adding their bathwater to soup, which, it was said, would function as a charm to make Tibetans convert to Islam.
"You hear all these stories about Muslims putting stuff in the soup. But I think it is all about business competition and economics," said Tsering, 37, a Tibetan businessman from Lhasa who did not want his last name to be published.
Making matters worse, the Hui usually support the Chinese government in its repression of Tibetan separatism.
"They think the Dalai Lama is their leader. But how is independence possible?" whispers Han Rugubai, a 26-year-old Muslim who sells clothing at Dawu's main market. "With the country developing so fast, life is good. People have enough to eat. They have clothes."
Han said she believed that the Tibetans' real quarrel was with the Han Chinese who dominate this country's population and politics.
"They use us as a scapegoat for their grievances against the country," she said.
In the last few years, clashes have broken out over the most trivial grievances. In February, a Tibetan child's complaint about what a Hui merchant was charging for balloons triggered a brawl that involved thousands of people.
Chinese troops intervened in a 2003 dispute that started over a game of billiards. A Tibetan and a Muslim died in tit-for-tat killings, the Muslim stabbed to death with a barbecue skewer.
Jia Han of The Times' Beijing Bureau contributed to this report.