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Gunman report sparks Nasa alert Gunman report sparks Nasa alert
(20 minutes later)
The US space agency, Nasa, has evacuated a building at the Johnson Space Center in Houston after reports that a gunman had been seen.The US space agency, Nasa, has evacuated a building at the Johnson Space Center in Houston after reports that a gunman had been seen.
A Nasa spokesperson could not confirm reports that shots had been fired - or that a man had barricaded himself in.A Nasa spokesperson could not confirm reports that shots had been fired - or that a man had barricaded himself in.
Police were called to the scene, an engineering office known as Building 44, at about 1340 (1840 GMT).Police were called to the scene, an engineering office known as Building 44, at about 1340 (1840 GMT).
They are said to have been once through the building and not found anything, but are conducting a new search. They are said to have gone once through the building and not found anything, but are conducting a new search.
The Houston police department told the BBC they had sent a helicopter, a canine unit and a weapons team to the Johnson Space Center. The Houston police department told the BBC they had sent a helicopter, a canine unit and a special weapons team to the space centre.
An intermediate school near the building has also been secured and parents have been told not to bring their children to the school. The centre's staff, numbering several thousand across the sprawling complex, were told to remain in their buildings.
An intermediate school near the building has also been secured and parents told not to bring their children to the school.
The alert comes less than a week after a gunman killed 32 students and teaching staff at Virginia Tech university before killing himself.The alert comes less than a week after a gunman killed 32 students and teaching staff at Virginia Tech university before killing himself.
The BBC's Adam Brookes in Washington says there has been a rash of security alerts across the US, which is also marking the eighth anniversary of the Columbine school massacre in which 15 people died.