About 200 people were trapped inside the 630-foot Gateway Arch for about two hours after an apparent power outage, authorities said.

The power went out around 8:45 p.m. Saturday, stalling two trams filled with about 40 people each, said Mike Maris, deputy superintendent of the Gateway Arch.

About 100 other people were stranded at the top of the monument of stainless steel, Maris said. He said the evacuation of the south tram, where one of nine cables may have broken, took about two hours.

Power eventually was restored to the north tram, and stranded visitors no longer had to use the stairs to evacuate, said Capt. Steve Simpson, a spokesman for the St. Louis Fire Department. He said officials do not know what happened to the equipment.

Simpson said rescue crews treated two people. One was given oxygen and the other was diabetic. He did not elaborate on their treatment.

"Everybody else seemed to be in good spirits, glad and relieved to be coming down," he said.

Anxious relatives stood outside the popular tourist attraction as rescuers worked inside. Dozens of emergency vehicles surrounded the arch.

Maris said the Arch would be open Sunday with only the north tram running.

The 630-foot-tall structure is operated by the National Park Service and opened in 1966. It is one of the region's most popular attractions.