Reports are that as the June 27 senatorial hearing about the West, Texas, fertilizer explosion is approaching, the Environmental Protection Agency has started responding to questions being posed by members of Congress.

A letter was sent to Sen. Barbara Boxer (D-Calif.), by an assistant administrator at the agency revealing that criminal investigators are determining if the plant’s operator complied with all regulations.

Apparently, Boxer and members of Congress have been asking why the EPA doesn’t regulate ammonium nitrate differently than current regulations, and the letter explains the EPA’s position.

A report on the letter and quotes from the regional office of the EPA are in a website report from the Dallas CBS television affiliate. To read the full report click here.