The U.S. Embassy in Bangkok is warning Americans of potential “violent retaliatory attacks” Friday after a group of 45 Uyghurs were deported by Thailand to China in a move Secretary of State Marco Rubio condemned in the “strongest possible terms.” 

Thai police and security officials said China had given assurances that the men — who had been in custody for more than a decade — wouldn’t face penalties or be harmed. They said at a news conference Thursday that all of them voluntarily returned after being shown a translation of a written Chinese agreement requesting their repatriation and declaring they would be allowed to live normally. 

“Similar deportations have prompted violent retaliatory attacks in the past,” the U.S. Embassy warned though on Friday. “Most notably, in the wake of a 2015 deportation of Uyghurs from Thailand, improvised explosive devices detonated at the Erawan Shrine in Bangkok killing 20 people and injuring 125 others as this shrine is heavily visited by tourists from China.” 

The Embassy is now encouraging Americans in Thailand to “exercise increased caution and vigilance, especially in crowded locations frequented by tourists due to the potential for increased collateral risk.” 

Thai soldiers inspect the scene after a bomb exploded outside a religious shrine in central Bangkok on August 17, 2015. (Pornchai Kittiwongsakul/AFP via Getty Images)

Thai lawmakers, activists and lawyers had raised the alarm Wednesday that the men were about to be deported, and after midnight, trucks with black sheets covering their windows left Bangkok’s Immigration Detention Center, where they had been held, according to the Associated Press. 

The news agency reported that it appeared the truck drove them to Bangkok’s Don Mueang airport, where a China Southern Airlines plane was waiting, and then flew to the heartland of China’s Uyghur population in northwestern Xinjiang province. 

In a statement on Facebook, the Chinese Embassy acknowledged Thursday that 40 Chinese nationals who it said entered Thailand illegally were deported to Xinjiang by a chartered flight. 

Police stand guard outside the U.S. embassy in Bangkok on Jan. 28, 2015. (Reuters/Chaiwat Subprasom )

It said the men had been detained in Thailand for more than 10 years because of “complicated international factors.” 

The Associated Press contributed to this report.