Hi Michael,

 

In addition to all the other answers that you have already received you can contact the "Museo de las Colonias Judias de Entre Rios" (https://es-la.facebook.com/museo.villadominguez/) who has a huge archive related to the people living in the colonies.

 

Also, if your relative arrived in Argentina through the JCA program, you can contact the Jewish Museum of Buenos Aires (http://museojudio.org.ar/) who has the archives with the JCA passenger lists. 

 

Best,

Ariel Parkansky