Update at 2:45 p.m.: Revised to include response from the Black Police Association of Greater Dallas.

Four Dallas police officers have been placed on administrative leave and more than 20 others are under internal investigations for their Facebook posts, police announced Friday.

Officers received letters notifying them of the investigations Friday, about a month after researchers with The Plain View Project published a database of years of public posts from eight police departments that the database’s creators said “could undermine public trust and confidence in police.”

The project, which prompted a swift response from some departments, collected posts from scores of active and retired Dallas officers. And of the more than 5,000 posts archived in the database, over 300 were from active Dallas officers. The posts included Islamophobic comments, racial stereotypes and jokes about police brutality.

In a written statement, Dallas Police Chief U. Renee Hall said investigators' preliminary findings show that 25 officers shared or posted material "that was determined to be a potential violation" of the department's general orders.

The department's social media policy states that officers "are free to express themselves as private citizens on social media sites" as long as it doesn't "impair working relationships of the Department, impede the performance of their duties, impair discipline and harmony among coworkers, or negatively affect the public perception of the Department."

Hall said the department takes "these matters seriously and we want to ensure the community that we will not tolerate racism, bigotry or hatred of any kind in our organization."

"The Dallas Police Department prides itself on maintaining the highest standards of ethics and integrity while providing service to the community without prejudice,” Hall said in the statement.

The department did not name the four officers who were placed on administrative leave Friday.

Bob Gorsky, an attorney for the Dallas Police Association, said earlier Friday that he did not have information on individual officers or posts under review.

Until more is known about the department's investigation, Gorsky said, he hopes "DPD will focus less on being the thought police and more on the real police needs of the city."

If officers are found to have violated the policy, they could face potential disciplinary action, including reprimand, suspension or even firing, according to the department's general orders.

Terrance Hopkins, president of the Black Police Association of Greater Dallas, said some of the posts in the database "are truly disturbing comments" that shouldn't be said "by law enforcement or by anyone."

Hopkins said a "thorough and fair investigation will separate the hate and biased comments from comments that simply express disappointment with the senseless acts of carnage officers see on a daily basis."

Several Philadelphia-based lawyers posted the database in June. The project's introductory missive calls for “fairness, equal treatment, and integrity” in policing.

Some police departments responded quickly after publication. In Philadelphia, more than 70 officers were pulled from the streets last month. Phoenix Police Chief Jeri Williams denounced the posts in her department, calling them "embarrassing and disturbing" shortly after the database went online, according to Phoenix's KSAZ-TV. Twelve officers have been placed on non-enforcement duty, Phoenix police spokesman Tommy Thompson said in an email.

In a June 7 statement on Twitter, Dallas police said they were working with the researchers to review which posts violated department policy.

Some of the Dallas officers' posts in the database celebrate police use of force. Others are critical of groups such as Muslims, women and transgender people.

Last month, the Council on American-Islamic Relations called for diversity training for all Dallas police officers in light of posts "peddling Islamophobia and glorifying racism and police violence."

Emily Baker-White, executive director of the Plain View Project, said in an interview that her team looked at the Dallas Police Department in part to explore racial divisions in the city after the July 7, 2016, downtown ambush that left five officers dead. In that attack, a black Army veteran targeted white officers at the end of a protest related to police shootings of unarmed black men in other cities.

Baker-White also said she wanted some variety among the cities in the database so they didn’t “look the same.”

“We wanted big and small, rural and urban so we could get a snapshot of what police-community relations look like,” she said.

Baker-White said she has had several conversations with Dallas police internal affairs investigators since the database’s publication and provided the department with additional data.

“We hope this is shifting the conversations in the department away from a them-versus-us mentality and into a community policing mentality,” she said.

Hall said she will continue to update the public on the investigation's findings.