They are BRAC Bank’s Alupatti branch Sales and Service Officer Sultan Nahid and Credit Card Officer HM Shahriar Alam.

Four officials of the bank were taken to Rajshahi Metropolitan Police's Detective Branch office by Rangpur District Police from their workplace before Thursday evening, Assistant Commissioner Sushanta Chandra Roy said.

Rangpur police freed two after initial interrogation, he said.

Nahid and Alam were taken to Rangpur on Friday morning, he added. 

Rangpur’s Kaunia Police Station Inspector Mamunur Rashid Mamun, who is investigating the case, said Nahid is a cousin of suspect Humayun Kabir Hira who had been arrested earlier.

Alam is a friend of Nahid and they reside in Sagarparha in Rajshahi, the investigator said.

“The 10-day grilling of Hira started on Tuesday. We’ve arrested Nahid and Shahriar Alam following information he gave (during questioning),” Mamun added. 

The number of suspects arrested in the case has now risen to four. The other is Rangpur metropolitan unit BNP activist Rashedun Nabi Khan Biplob.

A colleague of the arrested bank officials said Nahid was from Lalpur in Natore district and Alam from Gurudaspur of the same district.
 
“I’ve heard that they were linked to [Islami Chhatra] Shibir when they were students. But I don’t have definitive information,” he added.
 
Japanese farmer Hoshi was gunned down at Kaunia in Rangpur on Oct 3, five days after the murder of Italian charity worker Cesare Tavella at Dhaka’s diplomatic zone. 
 
Police and witnesses said there were three assailants in both the murders and they fled on motorcycle.
 
Radical group Islamic State has reportedly claimed responsibilities of both the murders - but the government denies.
 
Hoshi lived in a house at Rangpur City’s Munshiparha. 
 
Police detained landlord Zakaria Bala, his brother-in-law Hira, rickshaw-puller Monnaf Ali, Rangpur city BNP Organising Secretary Anisur Rahman Laku and activist Biplob, and Murad Hossain, who resides in a house next to the crime scene.
 
Hira and Biplob were later shown arrested in the case police filed.
 
Police said the others were ‘still being questioned’, but did not confirm if they would be implicated in the case.
 
Hoshi’s body is now at Rangpur Medical College Hospital mortuary.
 
The Embassy of Japan has asked the authorities if it is possible to bury him in Rangpur.
 
Rangpur’s acting Deputy Commissioner Mostain Bilah has said no decision on the matter has been taken yet.