The flood struck Monday afternoon while a group of seven people were in Keyhole Canyon, a narrow canyon formed by water wearing through rock over the centuries, the park service said.
Eaker said search teams found the seventh body Thursday morning in Pine Creek Canyon, one of the park's "more technical," difficult-to-reach areas. They had not searched the area, located downstream from Keyhole Canyon, earlier because of the threat of more flash floods, he said.
The people in the group were between 40 and 50 years old and from California and Nevada, park spokeswoman Alyssa Baltrus said.
The park service has not identified any of the victims but the sheriff's department in Ventura County, California, said in a statement that one of the people killed was Steve Arthur, a sergeant and 21-year veteran with the department.
His wife, Linda Arthur, was the last person missing, the sheriff's department said.
The park service regularly warns people about the possibility of flash floods, according to the park Facebook page.
"All individuals who pick up permits are given safety information, including the current forecast and flash flood potential rating at the time they pick up the permit. Once inside a canyon, there is no way to contact individuals of changing conditions. When an incident like this occurs, a Search and Rescue Team will enter the canyons when it is safe to do so to prevent further loss of life."
The Virgin River rose rapidly as more than six-tenths of an inch of rain fell within one hour on Monday afternoon, the park service said.
A flash flood warning was established and all the canyons were closed, but park rangers could not get word to people in the canyons, Park Ranger Therese Picard told CNN affiliate KSTU of Salt Lake City.
The victims' vehicles were found on Monday evening and search efforts started Tuesday, the park service said in a statement
. Continued high water has hindered the search.
Known for its spectacular canyons and rock arches, the 150,000-acre Zion National Par
k is located in southwest Utah near the Nevada and Arizona borders.
"Keyhole Canyon is a short, narrow slot canyon located on the east side of Zion National Park," the park service said. "A permit is required for traveling through Keyhole Canyon and individuals must complete several short rappels under 30 feet and swim through several pools of water."
The same storm that sparked the flooding in the park also caused flash flooding near Hildale, which killed 13 women and children in two cars that were washed away by the raging waters.