LAS VEGAS — Utility officials blamed a transformer failure Wednesday for a power outage that affected four Las Vegas Strip resorts and left dozens of people stuck in elevators for more than an hour.

No injuries were reported among people who remained in elevators until firefighters and hotel staff members reached them at the Mandalay Bay, Luxor, Excalibur and Four Seasons hotels, fire and hotel officials said.

"We had equipment failure," said Chelsie Campbell, a spokesman for Nevada Power Co., the regional utility serving the Las Vegas area. She declined to specify the exact cause of the outage, which was reported with a minor explosion shortly before 8 p.m. at a transformer facility just east of the Strip.

Casinos remained open and operating with reserve power, and officials said generators provided electricity for security and essential hotel functions at the properties, which total more than 13,000 rooms and are operated or managed by casino giant MGM Mirage Inc.

"When we lost power, backup generators kicked in immediately just as they were designed to," MGM Mirage spokesman Gordon Absher said. "Those generators give us functioning power, but not full power."

Normal power was restored within 90 minutes to the Excalibur and neighboring pyramid-shaped Luxor. Full power was not restored to the 43-story Mandalay Bay until after midnight, Campbell and Absher said.

The Four Seasons has a separate entrance at the Mandalay Bay, and 424 posh rooms on floors 35-39 of the Mandalay Bay tower.

Absher said a limited number of elevators kept working at the hotels, and staff members provided flashlights and glow sticks to help guests who wanted to go to their rooms.

"Most people were pretty understanding," he said.