The district administration later made arrangements for them at another plush hotel in the city.
"An official from the deputy commissioner's office had visited us to book rooms for the prime minister and his staff, including security personnel, but we were not in a position to do so as most of the rooms were booked for a wedding reception," the hotel General Manager Joseph Mathias told PTI.
PM Modi's arrival coincided with the wedding reception yesterday evening, Mr Mathias said.
The three rooms that were available were not enough for them, he said.
"Considering security reasons, it was not advisable to book just three rooms for a big staff," he added.
However, the district administration made alternative arrangements. PM Modi was accommodated at Hotel Radisson Blu, where he stayed overnight and Monday.
There, too, the hotel management was said to have advised a businessman's family to reschedule the wedding reception, citing security issues, so that it concluded before the prime minister arrived.
PM Modi arrived Sunday night for engagements at Jain piligrim centre Shravanabelagola in Hassan district. His itinerary also included a South Western Railway function here and a public rally organised by the BJP in the run up to the Assembly polls in the state.