A worker at the city Board of Elections was discovered dead in a Bronx office Monday, officials said.

The 56-year-old woman’s body was found face-down in the ladies’ room at a board facility on Grand Concourse near Morris Avenue at around 9:20 a.m., police said.

The woman had last been seen alive by her co-workers at the office Saturday.

“They all worked until 9 p.m. on Saturday, and [a cab was called] to take them home,’’ the victim’s friend, Ana Vincenty, told The Post.

“Gina was going to leave with them, but when she didn’t show up . . . They just thought she took another cab and left,” Vincenty said.

A worker with the Medical Examiner’s Office said the woman, whose full name was not released by cops, appeared to have died of natural causes.