The victims of yesterday's Narayanganj five-murder incident died due to head injuries, according to autopsy reports.

Residential Medical Officer (RMO) Md Asaduzzaman of Narayanganj General (Victoria) Hospital told The Daily Star that the culprits beat the five with heavy substance indiscriminately on the upper parts of their bodies.

"Most of the injury marks were found on their heads. They died due to head injuries. No sharp weapon injury was found in their throats."

Earlier it was reported that the children were strangled to death while the adults were found dead with their throats slit.

Today, a case was filed against several unknown people in connection with yesterday's killing of five members of a family inside their home in Narayanganj.

Shafiul, husband of slain Taslima Begum, filed the case with Narayanganj Sadar Police Station, Officer-in-Charge (investigation) Shahjalal told The Daily Star.

Last night, police recovered five bodies from the ground floor of a five-storey house in the city's Baburail area.

The victims are: Taslima, 35, her son Shanto, 10, her daughter Sumaiya, 5, brother Morshedul, 22, and sister-in-law Lamia, 25.

Police said that Taslima's sister-in-law Hazera Begum went to the house around 9:00pm, found the door locked from the outside and could not reach the family over the phone.

Suspecting something to be wrong, she along with the neighbours broke into the flat, discovered the bodies and called in the law enforcers, said police.

Police reached the spot around 10:00pm and recovered the bodies.

The law enforcers picked up two relatives, including Lamia's husband Sharif for questioning. Sharif works at a mobile phone shop in the capital, Dhaka. On Friday, he went to Narayanganj.

Additional Superintendent of Narayanganj Police Mohammad Zakaria told The Daily Star that the murders were probably committed between noon and early evening yesterday.

He said they found two of the bodies in one room, on a bed and on the floor and three others were recovered from the floor of another room.

Residents of the adjoining flats told police that they did not hear or see anyone from that house since yesterday morning.

Khandakar Mahid Uddin, Narayanganj superintendent of police, said a family feud and money could be the reasons behind the murders.

He said the killers were possibly known to the victims. Nothing from the flat had been stolen or been damaged he added.