STORY: The complaint against 75-year-old party president and her son, Rahul Gandhi was lodged nine years ago by a member of parliament from Indian Prime Minister Narendra Modi's Bharatiya Janata Party (BJP).
Rahul Gandhi, who is also a senior figure in Congress, was questioned several times last month in connection with the same case. They have both denied any wrongdoing.
Protests erupted across the country as Sonia Gandhi appeared before the Enforcement Directorate. While Congress workers and supporters in New Delhi raised slogans and climbed on barricades, protesters with placards and flags marched on the streets of India's western Mumbai city to condemn the Modi-led government.
Security personnel were forced to use water cannons and detain protesters in New Delhi to control the crowd.