General Jose Lemus, commander of Ciudad Juarez's military garrison, said the tunnel "must have taken a long time" to build, suggesting "it could have been one or two years".

A secret tunnel discovered last week on the U.S.-Mexico border will be sealed by Mexican authorities, an army official in Ciudad Juarez said Saturday.

A clandestine tunnel discovered on the US-Mexico border allowing entry from Ciudad Juarez into the Texan city of El Paso will be sealed by Mexican authorities, an army official said Saturday, adding that its construction was under investigation.

Security has been ramped up on both sides of the border ahead of the inauguration of Donald Trump.