No shooter found at US Navy Yard in Washington

Authorities completed their investigation of the Washington Navy Yard following reports of an active shooter there Thursday morning, and reported that the area was “all clear.”

The Washington, D.C., Metropolitan Police Department confirmed to Al Jazeera that they found no shooter following their search.

Authorities said Thursday no injuries were reported at the U.S. Navy Yard in Washington after the facility was placed on lockdown following reports of a possible shooter, according to media reports.

A shooter had not been found as police swarmed the Navy Yard, according to a local CBS radio station, amid heightened security concerns ahead of the July Fourth holiday weekend.

“The FBI is responding to possible active shooter … situation, along with local law enforcement, at the Navy Yard," a FBI spokesperson had earlier told to Al Jazeera.

The FBI did not provide any additional information or confirm reports that shots had been fired. Citing an unnamed official, The Associated Press reported that shots were heard in a campus building.

Live television showed a massive police presence in the area, and more than eight blocks of nearby roads were shut down as authorities responded to the scene, the Metropolitan Police Department said.

The Department of Homeland Security and the FBI have issued an alert calling for local authorities and the public to remain vigilant for possible threats during the holiday weekend.

The Pentagon ordered new security measures put in place after a 2013 shooting at the Navy Yard. Aaron Alexis, 34, a former sailor who was working for a government technology contractor at the facility, opened fire on Sept. 16, 2013, killing 12 people. He was shot to death after an hour-long exchange with police.

Alexis had reported hearing voices and being unable to sleep in the weeks leading up to the rampage. The FBI said Alexis believed electromagnetic waves had been controlling him for the months before. He had had prior brushes with the law after firing a gun but the charges against him were dropped.

The Navy Yard, in southeast Washington, is the country's oldest naval installation.

Al Jazeera and wire services