Both machines were withdrawn a week ago after failing to detect heroin capsules hidden inside a passenger's body.
Last month, a passenger from Afghanistan had passed out after boarding his flight from Delhi and was offloaded. "He was rushed to AIIMS, where ultrasonography revealed 56 heroin capsules concealed inside his stomach that the scanner had failed to catch," a CISF official said.
Home ministry sources said the civil aviation ministry had been asked to buy more "sophisticated" scanners to avoid such lapses in future, and that an American company had been approached.
