"There was the odor of gas in the air," Flickinger said.
Hotel spokeswoman Crystal Sablan said all guests in all buildings were evacuated, then allowed to return after being given an all-clear by authorities.
Flickinger said the entire hotel was searched for bombs by canine units, then cleared.
About four hours after the blast, hotel guests milled about in its lobby while yellow caution tape cordoned off the entrance to the Tree Bar. Some guests went up and down in the hotel's elevators, and a small cafe in the hotel was open. Tour agents in aloha shirts waited for guests to arrive.
Ayaka Mita, an intern for the hotel who helped communicate with Japanese tourists who didn't speak English, said she was telling guests who asked about the situation "that the alarm went off and everyone had to evacuate."
The blast happened near a koi pond near the hotel's Tree Bar, which overlooks the hotel's gardens and features fire dancers as nightly entertainment. The hotel has been undergoing recent construction.