The Maharashtra government and the Mumbai Police have been given this information by the Intelligence Bureau.
The police has been asked to ensure that owners of luxury buses carefully check the identities of all passengers travelling on the Mumbai-Ahmedabad highway. The police has also been told that luggage must be carefully screened. Bus owners have been told not to accept any parcels mid-way.
This alert comes just days after intelligence agencies warned that terrorists may try to use a small plane or helicopter to target Mumbai's Chattrapati Shivjai airport.