Get the latest military news and headlines delivered to your inbox every weekday morning.
A group of 68 US lawmakers on Thursday demanded Mexico take all possible measures to ensure the safe return of a former US marine, jailed after crossing the border with an antique shotgun.
Jon Hammar, 27, a veteran of the wars in Iraq and Afghanistan, was arrested after entering Mexico on his way to Costa Rico for a surfing vacation. In Mexico, shotguns are reserved for use by the armed forces.
The US lawmakers insisted Hammar's case "is of the utmost importance," alleging the former soldier has been mistreated in prison, according to the letter released by Republican congresswoman Ileana Ros-Lehtinen.
According to the letter, Hammar was told by Mexican customs agents he was allowed to bring the gun, which he inherited from his grandfather, into the country as long as he registered it immediately with authorities.
"We would like to know how this could have happened, and why the (Customs and Border Protection) agents at the border gave Jon what was obviously wrong information," the letter continued.
The lawmakers write that Hammar, who has been treated for post-traumatic stress disorder after his deployments in Iraq and Afghanistan, has faced beatings and other abuses from fellow prisoners.
"His parents immediately began receiving extortion calls from these inmates," the letter states, adding "the inmates even forced Jon to speak to his parents on the phone and tell them to pay the money or he would be killed."
His family has also accused Mexican prison authorities of repeatedly handcuffing Hammar to his bed, which Mexico denies.