The company generated high priority targets using results from drilling last year, downhole electro-magnetic surveys, sampling and geophysics.
"We look forward to a very active 2019 as we still have cash reserves to cover the planned drill programme," president Jason Gigliotti said.
Sienna reported having about C$460,000 (US$343,000) in cash and equivalents at the end of March and a working capital deficiency of about $486,000 (US$363,000).
It had amended its agreement in March with a subsidiary of EMX Royalty Corp, to extend its option over Slättberg to October 31 and spend at least $250,000 (US$186,000) within the new period.
Sienna was originally to earn 100% of the project by spending at least $500,000 (US$373,000) within a year and issuing EMX 3 million shares, according to an agreement struck in December 2017, which was later extended to February 2019.
On exercising the option, Sienna is to issue a further 3 million shares and EMX will gain a 3% NSR.
Sienna increased its Swedish landholding to 12,733 acres last year and the project now contains 16 historic mines.
Sienna shares gained 22% or C1c yesterday to close at 5.5c, at the lower end of its 52-week range of 4-10.5c, capitalising it at $2.9 million (US$2.1 million).