Two of the 19 people killed in a prison riot in the Mexican border city of Tijuana on Wednesday were US citizens, a spokeswoman at the US Embassy in Mexico City said on Friday.
Over twenty inmates died and several dozen were wounded in back-to-back riots in the overcrowded Tijuana prison.
Tensions first broke out on Sunday during family visiting hours in the La Mesa jail after a prisoner died inside, apparently abused by the guards.
Four inmates died in the first spate of clashes and another 19 were killed in new rioting on Wednesday. Many others were injured.
"Two of the dead and three of the injured are American citizens," said the embassy spokeswoman. She said she did not know the names of the dead or where they were from.