As she entered Target Field through Gate 14 on Monday, a woman with two titanium knees set off one of five metal detectors being used for the first time at the Twins ballpark. One man triggered flashing red lights with his pacemaker. Another was stopped because of his steel-toed shoes.

Many fans said they were aware that metal detectors would be used at entrances to Target Field. But only those entering Gate 14 had to walk through the arbors of flashing lights and lift their arms as security personal waved metallic wands.

Cans of beer were the most common items confiscated. One man was stopped for having a small microphone deep in a pants pocket. Most other stops were because of cellphones. Metal I-phone cases were a particular problem.

Timothy Farrell, normally a corrections officer at the Oak Park Heights prison, was among the first wave of security personnel to work Gate 14 on Monday.

“When they first opened the gate at 1 p.m. it was a little chaotic,” he said. But people quickly adapted to placing personal belongings in a basket and walking through one of the five detectors.

Don Rackert, 71, of Roseville, didn’t make it through uninterrupted. His glasses set off the detector.

Peggy Driscoll, 52, of Morristown, Minn., was momentarily separated from her niece, who had a stroller and had to enter through a Gate 14 passage that had no metal detector.

“I didn’t expect to go through this,” Driscoll said. “It’s good, though. These days, you can’t trust anybody.”

Others were stopped for carrying keys or wearing watches.

Metal detectors are expected at all five Target Field gates by the end of the month. But the Twins want to gradually phase them in, said Patrick Forsland, the team’s director of guest and premium services.

By 2:45 p.m. — 25 minutes before the first pitch — the wait to pass through Gate 14 was two to five minutes. “I’d rather they do this than have a crisis,” said Sue Nicholas, 62, of Roseville.

Brent Snyder, 35, whose watch set off the red flashing lights, wondered if the metal detectors were really necessary. Chris Kororouski, 24, of Savage, waited behind the man whose pacemaker set off the alarm, and noted that the lines seemed longer than normal, even for Opening Day.

Chad Lassen, 36, of Farmington, said he went through a metal detector earlier this year at an NBA game in Brooklyn. John Stempfley, 61, of Holland, Mich., was not a fan of the detectors and the brief lines they produced.

“We don’t do that in Detroit or Chicago,” Stempfley said.