Mei Xiang, the National Zoo's female giant panda, gave birth to a cub Sunday night, the zoo says.
Staff at the zoo hasn't seen the cub yet, but can hear it.
"I'm cautiously optimistic as we haven't seen the cub yet, but we know that Mei is a good mother. Like everyone else, I'm glued to the panda cam for my first glimpse of the cub!" says Dennis Kelly, director at the Smithsonian's National Zoo, in a news release.