Except as otherwise provided by law, the person in active charge of any establishment or work place coming under the jurisdiction of the Labor Commissioner shall forward by mail to the commissioner at his office, within fifteen days after each accident resulting in serious physical injury to an employee while at work in such establishment or work place, a written notice of every such accident of which he has knowledge, which notice shall state the name of the injured employee, the time of the accident and the nature of the injury and shall also contain a general description of the location in the establishment and of the character of the machine, if any, upon which the employee was at work at the time. The commissioner shall forthwith transmit to the person in charge of such establishment a written acknowledgment of the receipt of such notice, and shall keep a record of such accidents thus reported to him. Such records, notices and reports to the commissioner and any investigation made by him or his deputies or agents shall be privileged and confidential and shall not be open for examination or inspection, and neither such commissioner nor any of his deputies or agents shall be a competent witness as to the facts involved in such accident in any proceeding pending in any court, unless such commissioner, deputy or agent was present at the time of the occurrence of the accident. The term “accident resulting in serious physical injury”, as used in this section, shall be construed to mean an accident which results in the death of the employee or causes his absence from work for at least one week. Any person, after having received from the commissioner forms for such notices, who fails to send notice of any accident as required by this section, shall be fined not more than twenty dollars.