Veteran Marxist leader and former West Bengal Chief Minister Jyoti Basu was put on ventilator on Wednesday morning after his condition turned serious. According to PTI, this was disclosed by the Debashish Sharma, Superintendent of AMRI hospital in Salt Lake, Kolkata, where Mr Basu is undergoing treatment. The Superintendent said that Mr Basu is under special observation at the ICU and special medical board has been constituted to review his condition. 96-year-old Mr Basu was admitted to the hospital on Friday last following a moderately severe pneumonic infection. <br/>The Prime Minister Dr. Manmohan Singh telephoned to the West Bengal Chief Minister Mr. Buddhadev Bhattacharjee to inquire about Mr. Basu's health this morning.