Arrested Tamil Nadu Minister V Senthil Balaji has undergone coronary angiogram and has been advised bypass surgery at the "earliest", the hospital treating him said on Wednesday.

The Electricity Minister was arrested by the Enforcement Directorate in connection with a money laundering case earlier in the day.

Balaji "underwent coronary angiogram at 10.40 am" on June 14, a medical bulletin issued by the Director of the Tamil Nadu Government Multi Super Speciality Hospital, Omandurar Estate, said.

"Coronory angiogram revealed triple vessel disease for which CABG (coronary artery bypass graft) - bypass surgery is advised at the earliest," it said.

The ED arrested Balaji under the Prevention of Money Laundering Act (PMLA), official sources said, making him the first minister in the M K Stalin-led government to face such an action from a central agency. Balaji was arrested after a long session of questioning, they said, even as the 48-year-old minister was admitted to a city government hospital after he complained of uneasiness.

He is likely to be produced before a special court later where the agency will seek his custody.

Chief Minister Stalin, who had already slammed the ED raids against Balaji on Tuesday as "intimidation politics", went into a huddle with his senior party colleagues today following the minister's arrest.

The ED had launched multi-city searches in the state on Tuesday at the premises linked to the DMK's Karur strongman as part of the probe into money laundering.

The action came months after the Supreme Court allowed a police and ED probe into an alleged cash for jobs scam against him.

Earlier, he was hospitalised after complaining of uneasiness, DMK leaders said. State Minister P K Sekar Babu claimed there were 'symptoms' that Balaji has been 'tortured'.

TV visuals showed Balaji being uneasy while being brought to the Government Medical College, Omandurar Government Estate in the city.

"He is in the ICU. He was in an unconscious state and did not respond when we called him by his name. He is under observation...there is a swelling near his ear. Doctors say there is variation in his ECG (electrocardiogram)... these are symptoms of torture," Babu told reporters.

Law Minister S Reghupathy, who visited the hospital, questioned the need for the ED raids at Balaji's house running non-stop for hours.

Youth Welfare and Sports Development Minister Udhayanidhi Stalin was among the cabinet ministers who visited the hospital. Meanwhile, central paramilitary personnel were posted at the hospital. Security was also beefed up in Karur.

The ED had launched searches at locations linked to Balaji at Chennai, Karur and Erode on Tuesday as part of the probe into money laundering.

Balaji was earlier with the AIADMK and had been Transport Minister in the late Jayalalithaa-led Cabinet.