New Delhi, Feb 15 (ANI): Deputy Commissioner of Police (DCP)-1 of New Delhi District, Jatin Narwal, on Monday said that they are investigating the threat call to CPI (M) leader Sitaram Yechury. He added that the written complaint has been received on the issue and legal action will be taken. He further said that number has been disclosed. The security around the CPI (M) office has been increased after this incident.