A passerby raised an alarm after spotting the bus with unconscious passengers near a check post in Saharanpur, some 575 km from here. The bus was coming from Bijnor and headed to Gangoh, a police official said.
The passengers were rushed to a nearby medical facility. The condition of 35 people is stated to be serious.
An eye witness said that a man has been arrested on suspicion that he drugged the passengers by feeding them drug-laced eatables.
"We have launched an investigation. Hopefully, more arrests would be made soon," a police officer said.