PROSPECT — The Maine Department of Transportation (MDOT) says it remains confident in the safety of the elevator in the 43-story Penobscot Narrows Observation Tower, although it left visitors stranded twice in eight days.

“There are an abundance of safety mechanisms on this elevator,” said Mark Latti, MDOT public information officer. “These safety systems did exactly what they’re supposed to do if they sense something is not quite right. We’re very confident in the safety of this elevator.”

Billed as Maine’s fastest and tallest passenger elevator, the trip from top to bottom takes about one minute.

It is the first bridge observation tower in the United States and the tallest in the world. Others are in China, Slovakia and Thailand.

On Monday at about 2:30 p.m. two visitors entered the elevator from the first level of the three-level observation deck at the top of the tower.

“The doors closed, the safety sensor sensed that something was wrong with the doors, and the elevator stayed where it was,” Latti said.

He said the doors stayed closed until a technician from Stanley Elevator Co., which installed and maintains the elevator, came to the scene.

Latti said in the meantime, six other people in the observatory were led down the stairs to the bottom.

Ken Sandhage, Maine manager for Stanley Elevator of Merrimack, N.H., said the technicians were able to get the elevator operating again and brought the two passengers down.

“We just go through the diagnostics on the elevator, determine what the problem is and come up with the safest, easiest solution to get the people out,” Sandhage said.

“We were able to identify the problem from the elevator equipment room and we were able to run the elevator down with the couple in it,” he said.

The passengers were stranded in the elevator for about one hour and 20 minutes.

On Sept. 21, Latti said, the elevator was headed down when it stopped about 1 foot before ground level. The doors wouldn’t open.

In that instance, local rescue workers freed the passengers. Other visitors at the top of the tower were guided down the stairs.

The elevator was closed for almost 24 hours following the incident Monday, but was operating again early Tuesday afternoon.

Latti said the problem Sept. 21 was related to calibration.

“It’s an incredibly tall elevator with only two stops, at the top and at the bottom,” he said.

“Most elevators have stops every 10 to 15 feet and recalibrate themselves at each stop,” he said. “But with such a long distance between stops — weight, temperature, humidity, all can factor in to how the elevator calibrates.”

“It can be difficult as weather conditions change. It can affect the elevator,” he said.

Latti said two instances of elevator problems in a tourist season is a very good record.

The department expects about 70,000 visitors will have taken the elevator to the top from the time the observatory opened May 1 until it closes for the season Oct. 31.

“We’ve gone through five months and tens of thousands of trips without the elevator stopping,” he said.

Latti said there were about four to five incidents last season when the observatory first opened, but the state worked with Stanley to fine tune the process to keep the elevator running.

The observatory is operated jointly by the Department of Conservation and MDOT.