The package was found at East Midlands airport, some 160 miles (260 km) north of London, from a US-registered cargo plane on its way to Chicago.
"We are urgently considering what steps need to be put in place regarding security of freight originating from Yemen. For security reasons there are currently no direct flights from Yemen to the UK," Home Secretary (interior minister) Theresa May said in a statement.
"We are working closely with our international colleagues and will continue to do so," she said.
May said the package originated in Yemen and was addressed to a destination in the United States. "At this stage there is nothing to suggest that any location in the UK was being targeted," she said.
The British government suspended direct flights from Yemen in January after a Nigerian "underwear bomber" with links to the Arab country allegedly tried to blow up a US airliner over Detroit on Christmas Day 2009.
Several media outlets reported that the package was a doctored ink toner cartridge containing white powder with wires attached to it.
London's Metropolitan Police, which took over responsibility for the operation from local police, said in a statement: "The plane stopped at East Midlands Airport as part of a routine stopover.
"Cargo removed from the plane was examined. Further tests were carried out. Following this a number of items have been sent for additional scientific examination."
Police confirmed that "explosives officers" attended the airport but that the airport "continued to operate as normal during the day."
