Nobel laureate Amartya Sen on Monday said there is a "reason to worry" over the communal violence that has engulfed pockets in Basirhat sub-division of West Bengal's North 24 Parganas district."Why is it happening? Is it because someone is inciting it? There is reason to worry over this," Sen told a television channel here when asked about it.The celebrated economist is in the city to attend the screening of a documentary on him by director Suman Ghosh.Violence erupted between two communities at Baduria on July 3 night over a Facebook post by a youth.While he was soon arrested, violence broke out with mobs attacking shops and houses, torching vehicles, including those of police, and putting up road blockades.Several police personnel sustained injuries as the violence to spread to various pockets under Basirhat sub-division.