At least one celeb-magnet Manhattan apartment building is stepping up security for package deliveries because of the mail-bomb plot unveiled on Friday, a source said yesterday.

UPS and FedEx packages for 15 Central Park West — home to the likes of Alex Rodriguez, Kelsey Grammer and Goldman Sachs CEO Lloyd Blankfein — are being diverted, the source revealed.

“They’re giving residents vouchers to pick up the packages at other facilities,” said the source, familiar with the building’s operation.

A building-management spokeswoman declined comment.

FedEx spokeswoman Sandra Muñoz said she had no immediate reports of package diversions from any Big Apple sites.

And UPS spokeswoman Karen Cole said it hadn’t changed any delivery schedules — “other than we suspended service to and from Yemen indefinitely.”