A state air monitor near the upper Minneapolis riverfront twice recently measured airborne particles at a level that violates the state standard.

The monitor is located is located on a rooftop just south of Lowry Avenue, and is sited across the street from a scrap recycling yard and its controversial metal shredder owned by Northern Metal Recycling at 2800 N. Pacific St.

Company President Stephen Ettinger said in an e-mail that he's been told that the state will need to evaluate about 17 companies.

According to the Minnesota Pollution Control Agency, the wind was blowing from the direction of the yard on both Oct. 26 and Nov. 1, when the violations were recorded. It said no violations have been recorded since.

However, the agency said it is still analyzing the type of particles that were captured by the monitor, which has been operating since the beginning of 2013. It said the source of the particles is likely to be within one-quarter mile of the monitor. It said that multiple sources may contribute to the violation.

The agency said that the violation involves total particles, rather than the more worrisome fine particles that can be inhaled into lungs more deeply.

The monitor was installed in response to community concerns about potential air emissions expressed when the agency decided in 2012 to modify the Northern Metal emissions permit, which a 2009 test showed that the company was violating. There was no immediate response from the company.