The post, by a college student named Akash Saha, sparked violence that led to attacks and arson of Hindu homes in the district on Friday, law enforcers said.
Akash was detained in Khulna on Friday, said Sheikh Abu Hena Milon, chief of Lohagara Police Station. More information about the incident would be made available later, he added.
Inspector Haran Chandra Pal of Lohagara Police Station said that Salahuddin Kochi of Dighlia village filed a case against Akash Saha on Jul 15, accusing him of belittling Islam. Akash was brought to court in connection with that case.
The 20-year-old Akash is the son of Ashok Saha and a resident of Shahapara neighbourhood of Dighalia village Ashok Saha was taken to the police station on Friday and has yet to return home.
Locals said a group of Muslims gathered in the area after midday prayers on Friday and started demonstrating against a Facebook post by Akash that allegedly offended Islam.
The mob turned violent in the evening. They vandalised several Hindu homes and torched one of them during the hate attack. The assailants also threw brickbats at a temple in the area.
Police fired warning shots to disperse the mob. The law enforcers took Akash's father to the police station after failing to find him. No attacker was detained at the time.
On Saturday, Narail-2 MP and former Bangladesh cricket captain Mashrafe Bin Mortaza visited the area and reassured Hindu residents in his constituency that their lives and property would be protected.
He sought the assistance of locals to ensure such incidents do not recur.
“This would not have happened if so many people had not gathered yesterday,” said Mashrafe.
“This is unprecedented in Narail. Those who live nearby should be ashamed because this is the place where such an incident started.”
The ruling Awami League lawmaker said people should have informed the police if they felt offended by Akash’s Facebook post. “Who are we to take action ourselves?”
“I call on you to come forward and help. Otherwise, we won’t be able to resolve this problem.”
Mashrafe had previously taken to Facebook earlier, saying the incident had “shocked” him.
“I cannot imagine that this is the same Narail that we have taken pride in since we were children,” he said.
After nationwide protests, law enforcers detained some of those involved in the incident.