Section 23A. Whenever the commission makes a finding that a holder of a license or permit issued under this chapter has violated any of the provisions of sections fourteen E to fourteen K, inclusive, of chapter ninety-three, the commission, for the first violation shall suspend such license or permit for a period of six days and shall, for the second violation, suspend such license or permit for a period of fifteen days, and shall, for the third and subsequent violation, suspend such license or permit for a period of thirty days. The commission may determine whether such a violation has taken place upon evidence secured by its own inspectors, investigators or agents, or from evidence submitted to it by any person or trade organization, or both. In investigating any violation by a licensee, the commission shall endeavor to avoid duplicating similar investigations by local licensing authorities.