The fundraising comprises a $3.2 million placement to undisclosed investors and a $2.7 million entitlement offer, with new shares being priced at 6c each.
El Zorro gold mineralisation has been classified as intrusive related and representing a "district scale gold system".
To date gold mineralisation has been proven over 1.5km of strike.
The next drilling campaign is set to comprise 4,000-5,000m in total.
Tesoro is led by geologist Zeff Reeves who has extensive experience in Chile and South America more generally.
Shares in Tesoro have recently been trading around 6.9c, capitalising the company at $25 million.
The stock was trading at levels around 2c early this year.