SAN DIEGO, May 23 (UPI) -- Five U.S. Marines have been killed in Southern California in the last eight days from non-combat causes, officials said.

The San Diego Union-Tribune reported Friday that three servicemen from Camp Pendleton and two from Twentynine Palms have been killed.

The confirmed or probable causes are homicide, suicide and traffic accidents, the newspaper said.

At least 13 Marines from the 1st Marine Expeditionary Force -- most of them stationed at Camp Pendleton -- have died this year. Most of the causes are believed to have been vehicle crashes, homicides and suicides.

By comparison, six Marines from Camp Pendleton have died from combat in Iraq during the same time period, Defense Department figures say.

"It's extremely unfortunate to lose any Marine, especially here in the states, where we should feel secure," said a senior officer for the 1st MEF who asked not to be identified because he wasn't authorized to speak about the cases.

"I can definitely say that the commanders and commands are looking into each one of these deaths to determine the cause, and then backtracking to see if we need to do anything different to avoid these things happening again," the official told the newspaper.