But Solid Energy said it had reconsidered its earlier refusal "in the light of public interest".
Contractors made up almost a third of those caught. Two had tested positive for P and nine for cannabis.
Solid Energy said it had "zero tolerance" for any substance that impaired the ability to work safely.
Solid Energy had not responded to questions about whether any of those caught were repeat offenders and how many, if any, were sacked, by the newspaper's deadline.
The company said last month that those who tested positive for the first time were referred to an external programme for support and could return to work when they had successfully completed it.
Anyone who tested positive more than once had broken their contract and would face further discipline.
Blanket testing is part of Solid Energy's standard drug and alcohol testing procedure. It includes random, causal and pre-employment testing at all its sites, including offices.
In 2008 drug testing at Stockton netted 18, mostly cannabis users, despite workers receiving a month's notice of the tests.
- NZPA