TEMECULA - A Lake Elsinore man who was rescued from a Temecula trench last week has died from his injuries, officials said Tuesday.

The 21-year-old man was pronounced dead at 11:30 a.m. Thursday at Palomar Medical Center in Escondido, a spokesman for the San Diego County medical examiner's office said. His death came three days after rescuers lifted him from the trench.

State officials also said Tuesday that an investigation into the incident is ongoing.

The man's name has not been released pending notification of family members, who are in Mexico, the spokesman said.

The cause of his death is listed as cardiopulmonary arrest and not receiving enough oxygen to his brain, according to the medical examiner's office.

The afternoon of June 11, he and another man operating a backhoe were digging a trench for a septic tank in the area of Estero Street and Ormsby Road. The man lost his footing and fell into the 15-foot hole, followed by a wall of dirt that completely covered him.

The backhoe operator jumped in and, using a shovel, was able to dig out his co-worker to the man's mid-thigh, freeing his head and upper body from the dirt, officials said.

Firefighters and paramedics arrived soon after and spent several hours shoring up the sides of the trench so the man could be safely rescued. Almost as soon as he was lifted from the hole, the man went into cardiac arrest.

Firefighters said such a response is common in rescues like this one because blood flow is cut off and the body builds up toxins that then can get into the heart once blood flow resumes.

Dean Fryer, spokesman for the California Division of Occupational Safety and Health, said Tuesday that the man's death does not change the agency's investigation.

"The only thing that changes is that now, when we complete our findings, we will pass it on to the (Riverside County) district attorney's office," Fryer said.

It typically takes state investigators about two or three months to complete an investigation such as this, Fryer said, adding that they have a six-month window to finish.

"We will be looking at things such as what safety measures should be in place and whether those were followed properly," Fryer said.

- Contact staff writer John Hall at (951) 676-4315, Ext. 2628, or jhall@californian.com.