According to The Times of India:
NEW DELHI: Following intelligence inputs that terrorists may launch a chemical attack by releasing toxic gases in aircraft and other modes of public transport, the Union home ministry has issued an alert to all states and security agencies to step up frisking and baggage checks at airports, bus stands, and train and metro stations.
The security personnel have been asked to be on a lookout for any substance that could be used to release deadly toxic gases on aircraft.
The MHA on September 1 wrote to all states, aviation ministry and other agencies: “Central security agencies have intimated that terrorists are planning a range of attacks against commercial aviation targets.”
The MHA alert follows a foiled bid last month in Australia to bring down a commercial aircraft. The Australian police had said that terrorists tried to place an improvised explosive device on a Gulf carrier’s aircraft .
The MHA alert said the terrorists could adopt chemical warfare capabilities to conduct chemical attacks by creating toxic gases from materials available at hardware store or from easily produced materials including chemical powders, pesticides, acids and water, disguised as medication, food, beverages or household cleaners .
“Toxic gases pose the greatest hazard when made in an enclosed space, underscoring the risk to aircraft, buses or trains,” says the MHA. Based on the alert, the Bureau of Civil Aviation Security has written to the top brass of CISF, Airports Authority of India and JV metro airports to step up security arrangements.