A new report from the Utah Highway Safety Office (UHSO) has found the number of fatal accidents involving drivers with detectable levels of cannabis in their systems to have “skyrocketed.”

According to the report, the number of fatal crashes involving drivers later found to have used cannabis has more than doubled in recent years, climbing from 6 percent in 2012 to 15 percent last year. That percentage increase amounts to a rise from 11 fatal crashes in 2012 to 38 in 2015.

In 2012, Washington became one of the first states to legalize marijuana. Now a study by AAA has found the number of fatal accidents involving drivers with THC in their system doubled between 2013 and 2014.

The study also found that there is currently no reliable test to determine the amount of marijuana in the blood stream that leads to driver impairment.

While officials are unsure of the cause, many speculate that it could be related to the loosening of cannabis laws in surrounding states.

“Regardless of the cause, we’re very concerned about it,” said Sgt. Christian Newlin, a member of the Utah Highway Patrol who monitors the UHSO’s programs involving drug recognition and breath testing.

The release of the report comes on the heels of the release of a report from the AAA Foundation. That report, released Tuesday, found the number of driving fatalities involving drivers with cannabis in their systems had doubled since Washington legalized recreational cannabis.

However, many observers caution that the apparent severity of the numbers may be misleading, since the use of cellphones while driving, they say, results in more casualties than the use of cannabis. They also note that cannabis can stay in a person’s system for days or even weeks, which makes the process of determining whether their driving was impaired all the more difficult.

Nevertheless, lawmakers in Utah have expressed a mixture of concern and caution regarding the increase in driving fatalities.

“We don’t know all of the ramifications,” said state Rep. Lee Perry (R-Perry), who was one of the representatives during the Utah Legislature’s battle over medical cannabis this year who cautioned that legalization could result in greater numbers of impaired drivers. “So to just go in and say, ‘Let’s just go do it and try’ is probably not the wisest policy decision.”