"The security agencies are checking the cargo," said airport spokesman Manish Kalghatgi.
The plane from Amsterdam landed at Mumbai's international airport at 11 p.m. and was immediately taken to an isolated bay, where it was being inspected by bomb squads and airport security, Kalghatgi said.
All 244 passengers on board Delta flight 70 were evacuated safely, he said.
"Delta staff in Amsterdam informed the pilot there may be unaccounted-for cargo on board," he said.
The airport remains on high alert, but other flights are operating normally, he said.
Delta Air Lines Inc. posted a statement on Twitter that read: "We requested rescreening of some cargo on flt 70 in Mumbai. Paxs deplaned safely & we are working with authorities."
Passengers were asked to remain at the airport until all luggage and cargo searches are complete, said Rohit Sharma, who was outside the airport waiting for a relative who was on the flight.
In Amsterdam, spokespeople for Schipol Airport and KLM, which has a code-sharing agreement with Delta, declined comment.
Two package bombs sent via air freight from Yemen to the United States were found in Britain and the United Arab Emirates last week. One was diffused just 17 minutes before it was set to detonate, according to the French interior minister.