LAS VEGAS -- Police in Las Vegas said they've arrested a Nevada Highway Patrol trooper involved in a fatal crash last month.

Police said Sgt. Edward Lattin had marijuana in his system when his vehicle veered into oncoming traffic in western Las Vegas and struck two other vehicles. The incident occurred at about 1:30 p.m. June 11 in the area of Rainbow Boulevard and Hacienda Avenue.

Details indicate Lattin was traveling northbound on Rainbow Boulevard when his vehicle struck a light pole and two other vehicles at the intersection of Tropicana Avenue and Rainbow Boulevard.

Three occupants of the two vehicles were transported to University Medical Center. One of the passengers, a woman identified as 49-year-old Ying Warren, was pronounced dead shortly after arriving at UMC. The other two occupants were treated and released.

Lattin was booked into the Clark County Detention Center on the charge of one count felony DUI/Drugs resulting in death after he surrendered to authorities Tuesday.

Authorities initially suggested a medical condition might have caused Lattin to black out behind the wheel. But police now say a blood test taken after the crash tested positive for marijuana.

Lattin is a supervisor who leads a team that investigates fatal accidents. He was not on duty at the time of the crash.

An NHP spokesman said Lattin has been placed on administrative leave while the agency investigates the incident.

The Department of Public Safety released a statement regarding the incident. The following is an excerpt from the DPS statement:

Although Lattin was not on duty at the time of the accident, and he was driving his personal vehicle, the Department of Public Safety has initiated an internal investigation into Sgt. Lattin’s conduct. Sgt. Lattin has been placed on Administrative Leave pending the outcome of the investigation, which is being conducted by the Department’s Office of Professional Responsibility (OPR).

Department of Public Safety Director Jerry Hafen stated, “Although this tragic accident did not occur while he (Lattin) was working, the Department of Public Safety has zero tolerance for substance abuse either on or off duty and we, as well as the public we serve, hold our police officers to the highest standards of conduct.” Hafen added, “If the findings of the case prove that Sgt. Lattin was driving under the influence of a controlled substance, he will no longer be employable by the Department of Public Safety.”