Upgrades are coming to University Medical Center, Nevada's only public hospital and the top-tier Level 1 trauma center serving the state and parts of Southern California, Utah and Arizona, officials said.

Work started Tuesday on a $55 million project to modernize the 92-year-old Clark County facility, hospital spokesman Scott Kerbs said.

The 541-bed hospital a few blocks west of downtown and the Las Vegas Strip is the third-largest by capacity in Nevada, behind Renown Regional Medical Center in Reno and Sunrise Hospital and Medical Center in Las Vegas. Kerbs said future work at UMC will add beds, but the number has not been specified.

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The facility was a key treatment center in October 2017 for victims of the deadliest mass shooting in modern U.S. history — the Las Vegas Strip massacre that killed 58 people in a concert crowd and left more than 850 people injured. Two other people died later.

During the next three years, the hospital will modernize building facades and lighting, add two "healing gardens," upgrade parking and pedestrian access and consolidate women and children services in one building.

UMC is the only hospital in the state with a trauma center, a hospital official noted to the Las Vegas Review-Journal. It also has a children’s hospital and a burn unit. Renown and Sunrise each have Level 2 trauma centers.