A group of immigrants died while illegally crossing the border from Mexico into San Diego on Monday.

The incident occurred near Mount Laguna in San Diego County, California.

NBC News reports that Border Patrol dispatch responded to a notification that five people were in need of medical assistance near La Posta Indian Reservation on Monday around 2.15pm.

The San Diego Sector Customs and Border Patrol characterised the area as "very rural and extremely rugged."

The area was especially treacherous Monday, as the National Weather Service out of San Diego earlier reported that there would be “heavy snow with poor visibility” on Mount Laguna.

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On Monday, between 4 to 5 inches of snow fell on Mount Laguna.

Mount Laguna is on the eastern edge of the Cleveland National Forest, which separates the western portion of San Diego from the Anza Borrego Desert in the west. The mountain is approximately 30 miles north of the border.

The San Diego Sector CBP reported that two of the five individuals were able to walk out of the area on their own. The pair informed the agents that three other individuals would need to be rescued.

Two hours later, helicopters managed to reach the other three individuals. Two were unresponsive and one was in serious condition.

San Diego Sector CBP said that upon arrival the responding agents provided medical assistance, but ultimately all three individuals died. Agents said the individuals were suffering from hypothermia.

The CBP said weather conditions forced them to wait to remove the bodies until the next day.