Police suspect that the motive was not to kill anyone but to threaten someone, possibly due to an internal conflict.
Paiboon Upatising, president of the Phuket PAO, claimed there was no discord within the organisation, whether over procurement or budget spending, and the PAO election had been over a long time ago, so it was unlikely that politics was involved.
Some people might be upset about the results of the recent bidding for space concessions, but the process was transparent, he said.
Police were alerted to the explosion near the PAO office within the Phuket City Hall complex in Tambon Talad Yai of Muang district at around 2pm.
Pol Col Saneh Kawila, deputy Phuket police chief, said police would continue to investigate this case, which should not concern tourism.
Security in the complex would be beefed up, he added.