According to police, glass panes of two windows of the building at Chembukkav area were found shattered in the stoning. There was no one in the building when the incident happened.
Police had taken a suo motu case as no complaint had been made against anybody about the stoning that happened last night, police sources said.
Significantly, the incident happened in the wake of a section of the party coming out openly against nomination of Abdurahaman Kutty, a protege of Chacko as the District Congress Committee (DCC) president.
Disgruntled party leaders and workers, mostly belonging to the faction known as "I", had yesterday come out openly against the selection of Abdurahaman Kutty.
They alleged Chacko, who represents Thrissur in the Lok Sabha, had lobbied for Kutty, spoling the chances of more senior leaders from the district, where the party was once controlled by the late veteran K Karunakaran.
Reacting to charges against him, Chacko said the list of KPCC office-bearers and DCC presidents were approved and announced by the Congress High Command.
Chacko said he was aware there had been some rumblings over the issue but that would subside soon as all in the Congress would finally go by the High Command's decision.