WASHINGTON  The Obama administration on Monday moved to tighten air cargo security, banning large toner and ink cartridges from passenger flights and demanding new inspections on “high risk” shipments headed to the United States on all-cargo flights.

The new measures, which were put in place as of Monday, are intended to prevent a repeat of a cargo plot last month. In that plot, printer cartridges packed with explosives were sent from Yemen via express-mail companies, with the intent of blowing up planes headed to the United States.

Security officials remain concerned that larger toner and ink cartridges present a hazard, because explosives could be hidden inside. The ban, which also was adopted on Monday in Canada, applies only to cartridges that weigh at least one pound  typically cartridges for office printers and copy machines. The ban affects checked baggage and carry-on luggage, and will be in place on certain all-cargo flights.