Three people are dead after a bus explosion in Shanghai. The bus was travelling along Guoxing Road and Shunguo Road with 50 passengers on board. China’s news agency Xinhua carries the story, but there are still no details as to whether it was an act of terrorism or just an accident.

The explosion comes on the back of a recent China travel alert from the United States government. The government warns travelers to China for the Olympics:

Any large-scale public event such as the upcoming Olympic Games may present an attractive target for terrorists. There is a heightened risk that extremist groups will conduct terrorist acts within China in the near future. In light of these security concerns, U.S. citizens traveling in China are advised to use caution and to be alert to their surroundings at all times, including at hotels, in restaurants, on public transportation and where there are demonstrations and other large-scale public gatherings. Consistent with our standard advice, American citizens are urged to avoid the areas of demonstrations.