Nationally last year the NZ Drug Detection Agency conducted 68,551 on-site drug screening tests, up 31 per cent from 52,124 tests in 2011, and 29,513 in 2010.
The agency's chief executive, Chris Hilson, said the rise in the number of on-site tests in 2012 showed more employers were taking workplace safety seriously.
Of the 68, 561 drug tests carried out by the NZ Drug Detection Agency in 2012, 6.4 per cent tested "non-negative" indicating the presence of drugs, compared with 7 per cent in 2011.
Mr Hilson said that most of the agency's testing takes place in the safety sensitive industry sectors such as forestry, transport, construction, freezing works, manufacturing, transport and waste.
Port of Tauranga chief executive Mark Cairns said he was in talks with unions about developing a formalised drug and alcohol policy for random drug testing of port workers.
"We haven't had a problem so far but safety at the port is paramount."
The port did pre-employment and new-employee drug testing, and testing could be carried out if there is reasonable cause to suspect drug taking.