Manhattan’s Port Authority Bus Terminal went into lockdown tonight amid a bomb scare, authorities said.

Two suspicious packages were spotted by a passer-by near the Greyhound bus terminal in the lower level of South Building at 40th Street and Ninth Avenue in Manhattan around 7:30 p.m. — prompting the NYPD bomb squad to swoop in to investigate, officials said.

One of the packages was found to be empty — and the other contained four novelty grenades, or replicas without explosives, sources said.

“No one would have been injured unless the box landed on your head,’’ one law-enforcement source chuckled.

The package with the toy grenades was intended to be mailed to someone, the source added.

The terminal, which had been briefly evacuated, was reopened by 8:50 p.m.