Airports across India were put on high alert yesterday after a warning that a plane flying to Europe or the US could be hijacked. Officials at the airport in the southern Indian city of Chennai tightened security for passengers boarding flights to Europe and the US, adding a second round of body checks using metal detectors. Security also was stepped up at New Delhi international airport, according to a duty officer. The additional security measures were put in place following intelligence reports, said an official at the civil aviation ministry. The official did not elaborate, but the CNN-IBN television station reported that a US internet center received an email saying there were plans to hijack a US or Europe-bound flight from India. The center handed the email to the FBI which informed Indian intelligence, the report said. The report did not say who sent the email or if any particular airport or airline was at risk. Only days earlier, a letter warning of imminent attacks at airports or on aircraft in southern India prompted officials to issue a security alert for airports there. The letter was sent to the director of the domestic airport in the southern city of Trichy. Authorities are investigating.