A man and a nine-year-old girl died after taking “herbal syrup” in Kushtia's Mirpur upazila on Sunday night.
Nur Mohammad, 50, and his neighbour Shamima Akhter, of Kharara village, died within hours after taking the syrup.
Father of the girl Nabab Ali, who also took the medicine, was admitted to Kushtia General Hospital.
They took the “energy boosting” syrup around the same time.
Nabab, a brick kiln worker, told reporters yesterday that local drug store owner Rajib Hossain sold a bottle of the syrup to him about two months ago.
He went to Rajib's pharmacy about two months ago and asked for something that could cure his weakness.
Rajib suggested that he took a small dose of the syrup named “Marigold” every day for a certain period. Nabab then bought the bottle for Tk 350.
“I stopped consuming the syrup after the first attempt as it made me dizzy,” Nabab said.
On Sunday night, Nabab's neighbour Nur, a day labourer, came to his house and after learning about the syrup, he wanted to try it.
“Nur and I consumed a small amount of the syrup around 8:30pm. I was compelled to let my daughter have it too as she kept asking for it.”
They fell sick around 10:00pm and were rushed to Bheramara Upazila Health Complex where doctors pronounced Shamima dead.
Nabab and Nur were taken to Kushtia General Hospital where Nur died around 11:00pm, said Taposh Kumar Paul, resident medical officer of the hospital.
The bodies were kept in the hospital for autopsies, he added.
Officer-in-Charge of Mirpur Police Station Abul Kalam said Rajib, locally known as a quack, had been detained yesterday morning.
The syrup will be sent to a laboratory in Dhaka for tests, he added.