LOS ANGELES (AP) — Thieves breaking into freight trains in Los Angeles have stolen guns from cargo containers.

The Los Angeles Times reports that police Chief Michel Moore told the city’s board of civilian police commissioners on Monday that “tens of firearms” have been stolen. Moore expressed concern that the firearms would be a source of further violence in the city.

The rampant theft from trains on Union Pacific tracks near downtown has at times left the tracks covered in a sea of discarded boxes, wrappers and unwanted items.

The Times reports that a Union Pacific spokesperson said the railroad has brought in dozens of special agents to help but declined to comment on the gun thefts.