The department says three Mexican migrants were also rescued when soldiers found the 37 men and 10 women Tuesday as part of their work against drug traffickers. A statement from the department says no one was arrested.
Reynosa is across the border from McAllen, Texas. It is in Tamaulipas state, where 72 migrants from Central and South America were slain last August in a massacre that authorities blame on the Zetas drug cartel.
The Zetas split early last year from the Gulf drug cartel and set off a bloody territorial battle in northeastern Mexico.