At least one person has been shot and wounded at the US National Security Agency's headquarters at Fort Meade, Maryland.
One person was in custody following Wednesday's shooting and officials have secured the area and there was no continuing threat, local media reported.
A Fort Meade spokesman confirmed one person had been injured and transported and that a main highway was closed near the facility, a US Army installation about 48km northeast of Washington.
The Federal Bureau of Investigation confirmed on Twitter that its Baltimore office had sent agents to investigate the incident, its Baltimore office said on Twitter.
Local media quoted an NSA spokesman as saying the area was now secure.
Earlier local media reports said that as many as three people had been wounded.
Local fire and police departments had said earlier on Twitter they were responding to a possible shooting incident.
The National Security Agency/Central Security Service is one of the US government's main spy agencies.
The secretive agency focuses on using technological tools, including the monitoring of internet traffic, to monitor the government's adversaries.
A White House spokeswoman said US President Donald Trump had been briefed on the incident.