Babu has termed Saturday's raid by the Vigilance and Anti Corruption Bureau as "political vendetta".
On Monday, the officials called in a personal staff of Babu, who was with him during the period he was minister between 2011-16.
On Saturday, the Vigilance had conducted simultaneous raids at the houses of two of Babu's aides in Ernakulam district and also at the homes of his two married daughters.
On Monday, the Vigilance opened the bank lockers of Babu's daughters.
Babu belongs to the faction in the Congress party led by former Chief Minister Oommen Chandy.
While Chandy has criticised the raids as "political vendetta", state Congress president V.M.Sudheeran, who objected to Babu contesting the May 2016 assembly polls from Thripunithura, has remained non committal.
Leader of opposition Ramesh Chennithala told IANS that the raid against Babu was clear vendetta.
Former Chief Minister V.S. Achuthanandan told reporters that the scams of the previous Congress-led UDF will be brought out by the Vigilance.
"All what the Congress leaders are saying against the raids is false," said Achuthanandan.
State Congress vice president M.M. Hassan termed the "silence" of Sudheeran as most unfortunate.
"The Kerala Pradesh Congress Committee is duty bound to come to the aid of Babu," said Hassan.
The raids started on an FIR filed in a vigilance court in Ernakulam district saying that Babu had accumulated wealth disproportionate to his known sources of income.
