Reward offered for US agent death in Mexico
The US government has offered a $5m (£3.1m) reward to find those behind a deadly attack on two US officials in Mexico.
Immigration agent Jaime Zapata was killed and his colleague Victor Avila was injured as they travelled from San Luis Potosi to Mexico City last month.
It was the first killing of an American official in Mexico in 26 years.
Several people have been held in connection with the attack, but the investigation remains ongoing.
The US state department said the reward money was funded by its narcotics rewards programme.
The Mexican government has also offered up to 10 million pesos ($839,420; £522,612) for information leading to an arrest.
Authorities in Mexico blame the Zetas drugs cartel for the deaths, and have already arrested several of its members.
In February, Mexican troops detained Julian Zapata Espinoza the alleged leader of the gang, known as El Piolin or Tweety Bird.
Mexican officials said he told them he and other gunmen had opened fire on the US agent's car believing it belonged to a rival gang.
In recent years violence between gangs on the US-Mexico border has escalated.
The San Luis Potosi area, where the attack happened, is being fought over by the Zetas and a rival group, the Gulf Cartel.
It is also on the route used by illegal migrants who are trying to reach America.
Jaime Zapata, 32, of Texas, had been assigned to the Immigration and Customs Enforcement agency human smuggling and trafficking unit at the US embassy in Mexico City.
More than 34,000 people have been killed in drug related violence in Mexico since December 2006.