NEW : At least 44 injured in blast , including some police officers , firefighters . NEW : Police say they are investigating the cause of explosion and that it is not related to a gas leak at plant. No asbestos in air , but it was detected in six of 10 samples of dust , debris . Department of Environmental Protection will continue to test debris .
NEW : At least 44 injured in blast , including some police officers , firefighters . NEW : New Jersey woman died from cardiac arrest , mayor says . No asbestos in air , but it was detected in six of 10 samples of dust , debris . Department of Environmental Protection will continue to test debris .