Police conducted a "manual search" of the police parking garage for a suspicious person, but did not find anyone, the department said via Twitter.
A second K9 search that was carried out as a precautionary measure also turned up no one, and police employees were allowed to enter the garage and get their vehicles, the department said.
After the department tweeted that "Out of an abundance of caution, officers searched the garage to ensure reports of a suspicious person was thoroughly investigated," Dallas PD Chief David Brown tweeted, "Great job by our officers!"
The department also said that reports of shots being fired and that the police headquarters were under lockdown were both incorrect.
The alert comes two days after at least 12 officers were shot, and five of them killed, in downtown Dallas Thursday night, with the shots raining down during a protest against the fatal shootings earlier in the week by police of two black men: Alton Sterling in Louisiana and Philando Castile in Minnesota.
Some of the officers in Dallas were shot in the back. Two civilians were also injured in the ambush-style shooting, police said.
Micah Johnson, 25, was identified as the suspected gunman. After barricading himself inside a building, Johnson told hostage negotiators he was angry about recent shootings of black men by police and that he wanted to kill white people, especially police officers. He also indicated there were possible explosives in the area, police said.
After the hours-long standoff with law enforcement, Jonson was killed by officers who detonated a bomb delivered by robot, which appears to be the first time the tactic was employed.