A five-member body constituted to probe the robbery found 5,000 fake ampoules of Dekonet worth about at Tk 5 lakh in storekeeper Zillur Rahman's cupboard.

Locals allege patients of the country's lone mental hospital were treated with the fake injections over the years.

Police arrested Zillur, his assistant Saidur Rahman and Cashier Abdul Gaffer and sources say they have confessed to their roles in medicine theft.

Zillur told police that he along with hospital medical suppliers Mustak Hussain and Ansar Ali had long been stealing medicine from the hospital.

The storekeeper and the cashier were sacked in the wake of the robbery which locals allege was stage-managed to hide theft and irregularities at the hospital.

The Bureau of Anti-Corruption and the National Security Intelligence are also probing the robbery in which medicine and property worth about Tk 31 lakh were stolen.

The condition of 363 patients at the hospital has deteriorated as they are virtually going without medicine since the heist.

Doctors told The Daily Star that essential drugs including Dekonet injection could not be given to the patients and medicine supplies to the outpatient wings were also cut.

Local police said hectic lobbying by some local ruling coalition leaders for Zillur was holding back progress in the robbery probe.

But the assistant superintendent of police in Pabna, Jahan Mian, dismissed the allegation, saying the probe was on.

On the motive for the robbery, he said: "The incident was a drama to distract people's attention from medicine theft."