Canadian police have arrested members of an alleged hit squad investigators believe was tasked by the government of India with killing prominent Sikh separatist Hardeep Singh Nijjar in Surrey, B.C. last June, CBC News has learned.

Sources close to the investigation also told CBC News that police are actively investigating possible links to three additional murders in Canada, including the shooting death of an 11-year-old boy in Edmonton.

Members of the hit squad are alleged to have played different roles as shooters, drivers and spotters on the day Nijjar was killed at the Guru Nanak Sikh Gurdwara in Surrey, according to the sources.

The men were arrested Friday during police operations in at least two provinces. Sources said investigators identified the alleged hit squad members in Canada some months ago and have been keeping them under tight surveillance.

Police are expected to announce the arrests and share some details of their investigation later Friday.