The bomb squad and Dallas Fire-Rescue's HazMat Response Team were called to the Dallas Police Department's headquarters Monday morning after a city mail courier spotted a suspicious bottle near the entrance.
Sources say the clear water bottle was wrapped in electrical tape and had a handmade wrapper.
Assistant Chief Randy Blankenbaker said there also appeared to be a note attached to the bottle with "some handwriting and information ... that might help us be able to track down what really happened here."
Police say crews removed the package, which was "found to be harmless" and people were allowed back inside the building Monday afternoon. South Lamar Street was also reopened after it was closed during a temporary lockdown.
The liquid was later determined to be water, but officials with the Dallas Police Department said they won't take chances after the attacks on police over the last two years.
In June 2015, the department’s headquarters came under attack when James Boulware opened fired from an armored van. He was then killed in a standoff with police, and four bags containing pipe bombs were found outside the building.
In July 2016, four Dallas police officers and a Dallas Area Rapid Transit (DART) officer were ambushed and killed by a sniper while monitoring a demonstration in downtown Dallas.
The attacks have added stress the officers and the department.
"So their vigilance is normally toward their safety of other people," Blankenbaker said. "But over the last couple of years with what's happened, it's become more and more important for officers to be vigilant about their own safety."
Dallas police associations have requested better security for years but the Dallas City Council has yet to provide the money for the improvements needed.