The Massachusetts Civil Service Commission ordered the Boston Fire Department on Thursday to fully investigate allegations that a firefighter made racist and otherwise controversial comments on social media, following the firing of one firefighter who faced similar allegations.

The decision issued Thursday instructs the department to investigate the allegations that a firefighter, referred to as “MG," wrote the “n-word” in a Facebook post and mocked a black homeless man in a separate Facebook photograph. Commission Chairman Christopher Bowman first raised concerns about the comments in his Aug. 29 decision affirming the firing of another firefighter, Octavius Rowe, for controversial social media posts.

“In summary, when the BFD is presented with evidence that a Boston firefighter has allegedly used the ‘n-word’ in a public posting, they should take every step possible to investigate the allegation and, if proven, take appropriate disciplinary action, up to and including termination,” the order issued Thursday states. “That has not happened here.”

The Aug. 29 order reaffirmed the decision to terminate Rowe in 2018 over a series of social media posts. The department found statements written by Rowe, who is black, calling the head of the Boston Urban League a “shoe-shine Negro,” referring to gay men as “homophiles” and lesbians as “lez-beasts," according to the commission.

But Rowe’s counsel gave with the Boston Fire Department two pages that appear to show posts from a Facebook account belonging to “MG.” The commission didn’t include any other identifying information about “MG,” except to say he is a current employee of the agency.

The first page shows a Facebook post calling other firefighters derogatory names and accusing them of taking credit for a rescue they shouldn’t have. The second page includes a post using the “n-word,” and referring to “all lives matter," according to the commission.

After receiving the materials from Rowe’s lawyers, the department asked Ed Dominguez, a private investigator, to look into “MG’s” social media activity. Dominguez wasn’t able to find the alleged posts on “MG’s" Facebook account, but he did find a profile photo that showed what appeared to be an image, shot from inside a vehicle, of an older black man standing outside holding his hands up, according to the commission. Dominguez said he believes the man is homeless and has panhandled since the early 1990s.

When brought in for a disciplinary interview, “MG” admitted writing the post about the other firefighters but denied writing the post using the “n-word.” He was not questioned about the Facebook photo. The department concluded it was unable to determine whether “MG” posted a racial slur. Officials gave him a written warning.

He was not asked about the Facebook photograph of the homeless man, the commission stated.

Bowman, the commission chairman, said the picture of a black homeless man should have been a “bright red flag” to the department and that “MG” should have been questioned about it. He also called the agency’s decision to accept “MG’s” denial that he Facebook post with the racial slur “problematic.”

“I am not satisfied that the BFD pursued the same due diligence regarding the allegations against firefighter MG that it did against Rowe,” the decision states.

Unlike the Aug. 29 decision, Thursday’s explicitly orders the department to complete its investigation of alleged misconduct referenced in the Aug. 29 order within 60 days. The agency has 10 days after the investigation is complete to report to the commission an update, including findings and recommendations.

Bowman recommended the agency investigate the firefighter listed as “MG” and take disciplinary action, including termination, if found responsible.

The allegations against Rowe, the subject of the Aug. 29 decision, date back to 2017 when someone tweeted at Boston Mayor Marty Walsh and Fire Commissioner Joseph Finn a graphic photograph allegedly posted by Rowe. The image showed a caricature holding the severed head of a man with the words “PRAISE NAT TURNER #natturnerday," but the version tweeted at the city officials cropped out the text.

Rowe was placed on administrative leave on Oct. 2, 2017. The fire department launched a probe into his social media history and found a series of homophobic and otherwise controversial comments. He was fired.

The commission’s decision affirms the firing, but says Rowe is one of several firefighters facing allegations of controversial social media activity.

The commission also highlighted the alleged comments of three other firefighters, referred only by their initials. One referred to “MD” allegedly called former President Barack Obama a “cop-hating terrorist," and a second called “JC” made sexually derogatory comments on Facebook about MSNBC host Rachel Maddow and U.S. Sen. Elizabeth Warren, according to the commission.

“MD” and “JC” left the Boston Fire Department before disciplinary hearings and interviews took place, but the charges remain pending if they ever decide to return to the agency.