Miami ? Most Cubans did not see Fidel Castro fall after a televised speech, but by Thursday morning street corners, living rooms and workplaces were filled with hushed chatter. “Did you hear?” Cubans asked each other.

The Cuban government’s confirmation that Castro fractured his left knee and right arm in his second public fall in three years further fueled speculation about the 78-year-old leader’s vulnerability and capacity to continue to rule.

“That’s all anybody is talking about,” a retired professor in Havana told The Miami Herald in a telephone interview. “There is a lot of uneasiness over this.”

Castro’s fall occurred Wednesday night after a speech at a graduation ceremony in Santa Clara, in central Cuba. He apparently tripped while walking off stage and fell hard toward a row of chairs. Although TV cameras and photographers on the stage recorded the spill, Cuban television did not broadcast the fall.

Castro was quickly helped up, took the microphone and assured a visibly troubled audience that while he had shattered his knee and perhaps an arm, he was “in one piece.”

“The Cuban population was not shown the fall,” the professor recounted. “What we saw was the audience. Some people in the front row were running. There was a few moments of silence. Then we saw Castro sitting and talking. He looked very bad. He was sweating and obviously bothered.”

The confusing footage ignited Cuba’s word-of-mouth grapevine and prompted frenzied calls to and from the island for a detailed account of what happened. Even Venezuelan President Hugo Chavez reached for the phone in the wee hours to check on his close friend, Agence-France Press reported.

U.S. State Department officials in Washington had little to say on the fall, but turned their noncomment into a jab: “We, obviously, have expressed our views about what’s broken in Cuba,” said spokesman Richard Boucher.

William LeoGrande, a Cuba expert at the School of Public Affairs at American University in Washington, said Havana was smart to inform the public.

“They certainly couldn’t hide this,” he said. “It’s one more reminder that he won’t live forever and, in the not-too-distant future, politics in Cuba will be politics without Castro.”

Thursday’s government statement said a medical exam showed Castro “is in a good general state of health and his spirits are excellent” and that he “is fit to continue working on basic issues in close cooperation with the party leadership and the state.”

“People who surround him have got to be thinking ‘What’s going to happen?”‘ said Ninoska Perez, a spokeswoman for the Miami-based Cuban Liberty Council. “Eventually, if it’s not this fall that brings an end to Castro, it will be the next.”