NEW DELHI: An alert was sounded at Indira Gandhi International airport here on Wednesday after authorities received a call about a "big balloon" hovering over it.The red and white balloon was spotted around 3.15pm by the patrol guards at Air Force Station located on Gurgaon-Faridabad Road. The balloon is said to be of about a metre in diameter.It was spotted flying at the height of one to one and half kilometers and was moving towards Aya Nagar IAF station in Delhi.Following this, the police control rooms in Delhi and Faridabad were alerted by the Gurgaon police control room.Police said the call centre of the Delhi International Airport Ltd (DIAL) received a call about spotting of the big balloon following which the airport was put on alert.DCP of IGI airport DK Gupta said all security agencies have been informed about the information though police has not spotted the object."The airport was put on high alert after the DIAL call centre received a call about a big balloon spotted near the airport this evening."The call was received around 5pm and the caller said that the big ballon was heading from the airport to Aya Nagar following which an alert was issued at the IGI and all security agencies have been informed about it," Gupta said.The security personnel are now searching for the suspicious balloon.A mysterious balloon-shaped object was shot down on Tuesday by a Sukhoi-30 fighter aircraft in Rajasthan's Barmer district, bordering Pakistan, after the IAF radar detected it. Defence officials today said that no no dangerous payload was found.(With inputs from PTI)