ST. PAUL — Authorities have arrested a couple in the thefts of around a dozen musical instruments worth thousands of dollars from three St. Paul colleges.

Investigators believe the pair stole a violin, a viola di gamba, a guitar, trumpets, saxophones and trombones from Macalester College, the University of St. Thomas and Hamline University in recent weeks. They were arrested Friday during a traffic stop in Richmond, and formal charges are pending. Police described the man and woman as a couple but didn’t say if they’re married.

The thieves apparently entered the schools, found the music departments, walked out with any instruments they could lay their hands on, and headed to a pawn shop, Sgt. Paul Paulos said.

“They would go in almost looking like students, go into the music room and take these instruments and would later pawn them,” Paulos said.

Paulos said they are also suspected in thefts at real-estate open houses in which they posed as potential homebuyers but left with valuables.

“I think they found a niche in expensive instruments,” said Mike Barrett, public safety department associate director at St. Thomas. “They blended in with the environment.”

Paulos said the suspects were identified via pawn shop videos and through driver’s licenses they presented at the shops. He said the 33-year-old man has pawned more than 100 items this year, including instruments, jewelry, electronics and power tools.

“If you’re looking at Craigslist and anything’s too good to be true, it’s probably one of these stolen items,” Paulos said.

Some stolen instruments have been recovered from pawn shops, Paulos said.

According to Macalester, two saxophones owned by the school stolen Nov. 9 and a school-owned bass viola da gamba stolen Thursday have a combined value of $7,500 to $8,000. A student’s saxophone with an unspecified value also was stolen there Nov. 9. St. Thomas reported two trombones stolen Wednesday and a guitar stolen Nov. 4. A $6,000 saxophone owned by the university is still missing. At Hamline, a violin valued at $1,000 was taken Monday, and a school-owned trombone disappeared last month.