Workers are using bleach in a bid to beat drug tests at Bay of Plenty businesses.
Latest figures from the New Zealand Drug Detection Agency reveal the number of workplace tests in the region has more than doubled in the last year.
There were 4458 in 2011, compared with 1711 in 2010, with 8.5 per cent positive.
The agency's Bay of Plenty general manager Leigh Sefton said the increase could be down to a rise in testing rather than offending.
He said more companies recognised the benefits of a testing programme, in terms of morale and productivity as well as safety.