Story highlights Sen. Elizabeth Warren visited Hillary Clinton's campaign headquarters on Friday, according to people in the room

Clinton was not at campaign headquarters when Warren visited today, according to sources

(CNN) Elizabeth Warren, a senator being eyed as a possible Democratic vice presidential pick, dropped by Hillary Clinton's campaign headquarters on Friday, according to people in the room.

Warren, who endorsed Clinton last week in an interview, mingled with aides, took photos with staffers and gave brief remarks.

"Don't screw this up," Warren said, according to attendees.

The senator also referred to Clinton as a "fighter," the same terminology she used when she endorsed Clinton last week.

"We've got one tough cookie who is going to be out there fighting on behalf of working families across this country," Warren said in her remarks, according to a video posted on Instagram.

Read More