OneBlood, a foundation that operates blood bank collection centers throughout the southeastern United States, put out a call early Sunday for donors with O-negative, O-positive and AB blood following the mass shooting at a gay nightclub in Orlando.

Police have said at least 50 people have been killed and 53 have been injured in the early-morning attack. On Sunday, volunteers posted pictures on social media of long lines at numerous OneBlood locations throughout the country, and the organization said it is extending hours at many of those centers.

In a phone interview midday, foundation spokesman Pat Michaels said the response so far has been “overwhelming, especially here in central Florida.” Michaels said that while he urged people with O-negative, O-positive and AB plasma blood to donate immediately, OneBlood is asking people with other types of blood to “please hold on until we can assess what else we need.”

“We have hundreds of people showing up to our locations,” he said. “We understand the sentiment that people want to help and that giving blood is a profound way to help, but we are asking those who have other blood types to give us some space for now.”

While many people sharing the call on social media have reported that OneBlood is allowing all men who have sex with men to donate — going against Food and Drug Administration guidelines — Michaels said that’s not true. He said OneBlood is continuing to adhere to the longstanding federal restriction on gay men from donating blood. Although the FDA recently updated its guidelines to allow men who have not had sex with another man within a year’s time to donate blood, Michaels said OneBlood’s system has not yet been updated to allow that, but it will happen later this year.

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