CASCO – The third fatality of an all-terrain vehicle user along a Maine highway this year likely was caused by speed and alcohol, state police Trooper Lucas Hare said Thursday.

James Gregor, 43, died after arrival at Maine Medical Center in Portland after Tuesday night’s accident. State police said Gregor’s ATV went off the Libby Road and struck a tree and large rock about a mile from his home in Casco.

A passenger, Tammy Grover, 31, whose residence was not immediately available, was injured and also taken to the Portland hospital, but her injuries were not considered life-threatening, police said.

State law prohibits ATVs from being driven on Maine roads and shoulders, but they are allowed to cross highways. Gregor’s was the third fatality involving an ATV user along a Maine road this year, said spokesman Stephen McCausland of the state Public Safety Department.

Figures on the number of ATV fatalities in off-road accidents this year were not available Thursday. Between 1993 and 2002, nearly 2,000 people were injured and 32 died in ATV crashes in Maine. Nearly half of those involved in crashes were 20 or younger, according to the Governor’s ATV Task Force.

The latest fatality comes weeks before a new state law regulating ATV use takes effect. Most of the regulations taking effect Aug. 31 seek to prevent riders from trespassing on private land and in taking ATVs into environmentally sensitive areas.

The law also seeks to promote safety. Riders ages 9 through 15 will have to complete approved training courses with a parent or guardian present if they wish to operate an ATV off their properties.