BILLINGS, Mont. -

Tests done at the state crime lab indicate driving under the influence cases involving methamphetamine use have quadrupled over the past four years.

The crime lab's recently-released toxicology report says that in 2011, it tested blood samples from 73 meth-positive DUI cases. In 2015, that number was 294. During that time frame, the mean concentration of meth in positive tests more than doubled.

The Billings Gazette reports meth also is showing up more often in other testing done by the crime lab in Missoula.

Urinalysis tests conducted on probationers and parolees returned fewer than 200 positive meth tests in 2011. That number rose to 550 last year.

The number of unattended deaths in Montana in which the deceased had meth in their system has also increased, from 20 in 2011 to 73 in 2015.