Press secretary Smith Toby told the BBC that on Wednesday two black snakes were found in the foreign affairs ministry building, his official place of work.
All staff have been told to stay away until 22 April.
"It's just to make sure that crawling and creeping things get fumigated from the building," Mr Toby said.
"The Ministry of Foreign Affairs hosts the office of the president, so it did an internal memo asking the staff to stay home while they do the fumigation," he said.
The office of the president has been based in the Ministry of Foreign Affairs since a fire in 2006 gutted the nearby presidential mansion.
A FrontPage Africa news website video shows workers trying to attack the snakes when they appeared near the building's reception.
"The snakes were never killed," Mr Toby said. "There was a little hole somewhere [through which] they made their way back."
Police and presidential security were seen guarding Mr Weah's residence in the capital Monrovia. A fleet of vehicles including escorts jeeps were parked outside.
Mr Toby said the Ministry of Foreign Affairs started to fumigate on Friday.
"That building's been there for years now, and [because of] the drainage system, the possibility of having things like snakes crawling in that building was high," he said.
The president is definitely returning to his office on Monday after the fumigation whether or not the snakes are found and killed, Mr Toby said.