They have been working at the National Institute of Standards and Technology (NIST), a US government research centre in Gaithesburgh, Maryland, on two semiconductor manufacturing projects and a ceramics processing project, said NIST spokesman Michael Newman.

The State Department has blacklisted these three projects and has put on hold four projects NIST is running in conjunction with its Indian collaborator, the National Physical Laboratory, all related to scientific standards.

Newman told UNI that the State Department had asked for a list of the projects with which researchers from Indian institutions were associated. The department decided on who should leave the country and conveyed the decision to NIST which is run by the Commerce Department.

Newman said the NIST did not believe the projectshad any direct link with India's nuclear weapons programme. Apparently, the seven scientists were asked to quit because of the institutions they represented in India.