CTV News has learned that police received a call over the weekend from a man alerting them about a threat to harm social workers testifying at the Phoenix Sinclair Inquiry.

Police issued a statement on Wednesday.

"We have received a complaint regarding this matter. The appropriate notifications have been made and we will not be providing any further details or comments,” said police.

While a motive is not known, sources say the caller may have recently been released from jail and is a member of a Winnipeg street gang.

The MGEU, the union representing social workers, is calling for increased security for social workers who testify.

"They are very worked up about this as you can imagine, being placed into a situation like this is devastating for people,” said Michelle Gawronsky, president of MGEU.

The Phoenix Sinclair Inquiry is examining Manitoba's child welfare system and the death of five-year-old Phoenix Sinclair.

She spent much of her life being moved between her parents and foster care. In 2004, her mother, Samantha Kematch, had the child living with her. Months later in 2005, Phoenix was beaten to death by Kematch and Kematch’s boyfriend, Karl McKay, after being subjected to exteme abuse.

In July, the inquiry's commissioner denied a union request for a publication ban on the identities of social workers who would be testifying. The union said the threats are proof of why a publication ban was necessary.

"It was our fear when we asked for the publication ban. It has come forward. Now, we're dealing with it strongly," said Gawronsky.

Unlike the Law Courts, the Winnipeg Convention Centre where the inquiry is being held does not have metal detectors.

"IKEA got eight officers and four cruisers and yet we've got social workers now that are out there at risk and we're not getting the same for them," said Gawronsky.

The union said some social workers have switched offices where they work as a precaution and a child intake agency has added security.

A spokesperson for the Commission of Inquiry issued a statement Wednesday afternoon.

“The Commission has been advised of a potential threat related to the Phoenix Sinclair Inquiry. We are further advised that the Winnipeg Police Service is continuing to investigate this matter,” said the spokesperson.

“The Manitoba Justice Department, who is providing security support for the public hearing of the Inquiry, has also been made aware of this matter. The Commission will be carrying on with its hearing schedule as planned.”

A spokesperson for Manitoba Justice said that since the threat, more sheriffs officers have been added at the inquiry.