WASHINGTON (AP) - Teams of panda fans are keeping a 24-hour-a-day watch on the National Zoo's giant panda, Mei Xiang to see if she might give birth.

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Scientists at the zoo detected a rise in hormone levels in May that could indicate the panda may give birth or end a false pregnancy by early July.
Mei Xiang was artificially inseminated twice in January

. But it's difficult to know whether a panda is pregnant or exhibiting signs of a false pregnancy.

Since early June, zoo veterinarians have been trying to perform ultrasounds several times a week. The zoo says Mei Xiang has not always been cooperative.

She is also exhibiting signs of a pregnancy, such as eating less, sleeping more and cradling objects.

But for now, it's too soon to tell.