At least 30 people, mostly cattle traders, fell seriously ill and became unconscious after having breakfast at an eatery in City Bypass Haat area on the outskirts of Rajshahi city yesterday.

The people went there from different parts of the country including Narsingdi, Sonargaon and Comilla to buy cattle ahead of Eid-ul-Azha, Detective Branch of Rajshahi Metropolitan Police Assistant Commissioner Iftekhar Alam told The Daily Star.

He, however, said no valuables were stolen from them. The victims' fellows took them to Rajshahi Medical College Hospital.

The food items, including beef and rice, were not stale, Assistant Prof Mizanur Rahman of the medicine department quoted the patients as saying.

Something was mixed with those, which caused their illness, he said.

Kamruzzaman said he felt a bad headache and pain in the stomach immediately after having the food items. Belal Hossain, another victim, echoed him.

Prof Mizanur said the patients were now out of danger after treatment.

Detectives detained Faisal Hossain, son of the eatery owner, and three of its staff,  said Iftekhar, adding that they were being interrogated to find out whether any gang were involved in the incident.

A sample of the food items of the eatery was sent to a Dhaka laboratory for test, said the police official.