A 240-yard-long drug smuggling tunnel under the US-Mexican border has been unearthed.
The six feet by two feet tunnel, equipped with lighting and ventilation, was discovered on Saturday when officers raided a business on the Arizona side of the border, which concealed the US entrance.
Three people were arrested, according to a statement about the US operation by federal and local law enforcement bodies.
The US raid was coordinated with the Mexican military, which entered an ice-making plant across the border, said the US statement.
The "sophisticated" tunnel, which was 55 feet underground, led from the Arizona town of San Luis to the ice plant across the border in Mexico in San Luis Rio Colorado.
The tunnel's US entrance was located in a storage room hidden beneath a large water tank, in a one-story "nondescript" building. US authorities had been monitoring the business since January due to "suspicious activity."
The discovery "is yet another reminder of how desperate these criminal organisations are and the extent they will go to further their drug dealing operations," said Doug Coleman of the US Drug Enforcement Administration.
"The DEA continues to work with our counterparts nationally and internationally to bring to justice these drug trafficking organisations as well as to block their smuggling routes into this country," he said.
Last November two major drug smuggling tunnels were found near the Mexican border with California in Tijuana, one of them 400 yards long and the other 600 yards in length.
Some 45,000 people have been killed since 2006, when Mexico launched a major military crackdown against the powerful drug cartels that have terrorised border communities as they have battled over lucrative smuggling routes.